some stuff based on my past week or two of laddering ~300 or so games:
A- -> A
I think Moltres is honestly crazy good and it's weird how people are sleeping on it so much. I've seen some say that Hippo's existence is tough for it but honestly it's not true at all, even max spdef Hippo (uncommon) can't comfortably switch into Moltres at all since if it takes any chip (from Molt's own U-turn even) it just can't handle 2 Hurricanes. Beyond that there really aren't many comfy switch ins at all, it's realistically limited to Nihilego and Slowking (which can't switch in safely if physdef). Moltres has such a nice matchup into top stuff like Skarmory, Aegislash and Scizor too, I think it's in a really great spot rn and should rise. Was the bane of my existence while laddering despite having SpDef Hippo + SpDef Slowking + Thundy.
A- -> A
Keldeo's finally in a good spot. Most teams can't really handle it thaaaat well, Amoonguss / Tangrowth are not rly good answers and Slowking is falling off a little bit while Primarina is uncommon for one reason or another. Salamence is no answer and in particular I think Keldeo's ability to just shred hyper offense is super valuable, not only is it insanely hard for them to take Pump (esp. if they drop Gyarados) but it also has very nice natural bulk & a great typing that lets it check the ever-dangerous Cloyster and Scizor and even stuff like Aegislash in a pinch. I feel like it's on par with Hydreigon which is another great special wallbreaker rn and should rise to meet it.
B -> B+
Saw a ton of usage during the UULT laddering phase which may just be because it's cheese-resistant but I think Registeel's in a good spot rn altho it is still very matchup fishy. Not a fan of how open this leaves you to Aegislash at all, especially SD variants, and as such it needs to be built around which I think limits it from the A ranks, but it's still very good. Lots of teams are just 6-0d by this on preview if they lack Aegislash / Chandelure / Hatterene / IDef Skarm / SD Cobalion / NP Togekiss, which seems like a lot but that's still a pretty small subset of mons and unless your entire team prevents Registeel from setting up you'll probably have some trouble with it.
B -> B+
Demon, bullies Skarm teams so hard and is really annoying to deal with once it gets going which isn't too hard for it to do. Think it's in a very good spot rn with Skarm's dominance & its ability to bully (at least somewhat) teams that rely on Aegislash / Scizor for it.
C+ -> B / B+
Unexpected I'm sure but yeah, I wholly support this and will give some strong reasoning as to why so that nobody just thinks I'm nomming up a meme mon that I like.
Noivern's main appealing trait is of course its Speed which is more valuable than ever right now. Since most Crobats aren't running max Speed (I sniped way too many with Draco on the ladder...), Noivern is the fastest Pokemon in UU. Being able to outspeed and threaten OHKOs or near-OHKOs on all of Scizor, Salamence, Thundurus-T, Zarude, Cobalion, Hydreigon, Zygarde-10%, Starmie, Nidoking and Azelf is something very few other Pokemon can boast. Not only can it do this, it can also switch into these Pokemon (sometimes situationally, sometimes consistently) - Zarude and Azelf (the most common set I ran into on ladder, at least, which was Psychic/Flamethrower/Energy Ball/U-turn) can be pivoted into all game long thanks to your speedy Roost, and while Stone Edge from Cobalion is annoying you can take pretty much any other move easily. On top of this, threatening defensive staples like Tangrowth, Skarmory and Amoonguss is very nice, it's a good Mach Punch resist so you can RK Conkeldurr and it also 1v1s stuff like Mandibuzz if push comes to shove. All of this while having excellent defensive utility (much of Salamence's utility is also shared by Noivern - the fast Roost makes up for lacking intimidate when switching into stuff like Zarude or Entei, though you do suffer a worse matchup against Excadrill - you also have equally "bad" matchups against Keldeo since, while Salamence can slow Roost on Secret Sword and thus not be weak to it, Salamence can't roost off Hydro Pump since it's 2HKOd, while Noivern can PP stall them.) As pif said in one of my ladder games, being able to reverse momentum on popular momentum grabbers like Azelf, Zarude and Raikou is super nice and pretty unique to it.
All of this sounds great and all, but it still does have the same flaws as ever. Primarina wholly invalidates your existence, and while that's not always a huge deal if you run into standard RestTalk sets, you do need to be extremely careful around Specs and SubCM (Specs less so since you can wear that down pretty quickly via U-turn + hazards for an eventual Noivern win, but SubCM is a big threat). Additionally it's not even close to a wallbreaker - it's pretty strong and can pop offensive Pokemon, but you're toast into stuff like SpDef Hippo/Slowking outside of just U-turning on them all game long. Checks without reliable recovery like Swampert and Tentacruel tend to be favourable matchups because Noivern is outlasting them long-term, but they do keep you in check temporarily which is frustrating of course. There are also some priority mons you just can't handle (Mamoswine, Life Orb Scizor specifically - Noivern actually does check non-LO kinda, Lycanroc), and being forced to click Draco can occasionally be a lose-lose situation, though this can all be circumvented with a little support. They are notable flaws though, which is why I don't think Noivern belongs in the A ranks - it's very good but it does need support.
Here are some replays to show I'm not just talking out of my ass:
https://replay.pokemonshowdown.com/gen8uu-1570599713 - Once I'm able to wear down my opponent's main check in Swampert, Noivern KOs Salamence and automatically wins the game. It's also shown to be a capable switch in to Keldeo, Scizor and Azelf, all situationally but ya.
https://replay.pokemonshowdown.com/gen8uu-1570597507 - Noivern KOs both Scizor and Moltres - both of my opponent's Zarude checks - early in the game, at which point it wins on its own (or would've had my opponent not forfeited) as soon as Hippowdon goes down to Zarude.
https://replay.pokemonshowdown.com/gen8uu-1569350215 - As soon as Hippowdon trades a Toxic on Slowking, Noivern has essentially won the game; it even pops a Crobat from full HP due to being faster than it.
https://replay.pokemonshowdown.com/gen8uu-1568530616 - Checks a bunch of Pokemon early game between Zarude / Cobalion / Amoonguss and ends up sweeping once Slowking is KOd.
https://replay.pokemonshowdown.com/gen8uu-1567623960 - KOs Hippowdon itself and then wins, you know the drill by now
https://replay.pokemonshowdown.com/gen8uu-1566924056 - Solos Mandibuzz at which point it can clean up the remaining 4 members of the opponent's team
https://replay.pokemonshowdown.com/gen8uu-1566848856 - Even in a nightmare matchup with Chansey + Primarina + Mamoswine, Noivern manages to sweep at the end by outspeeding and deleting a Crobat, finishing up Zarude and Azelf afterwards
It's a good Pokemon! Speed is super vital in this tier and realistically Noivern hits the hardest out of the >115 options we have, being a reasonable amount stronger than Crobat and harder to wall since it can actually hit Steel-types for non-negligible damage and doesn't give free turns to the best Pokemon in the tier. It's seeing lots of use in Open and Ladder Tour even if that's primarily on the sample team that features it, and it's been doing great. It's significantly better than all the niche shit in C+ and in my opinion is better than everything in B outside of maybe Registeel and Hatterene which should rise anyway.
B -> B+
I've been shredded enough times by Specs Togekiss to respect it but I think the offensive Nasty Plot sets I've seen on the ladder w/ Air Slash + Flamethrower are sick. Nothing really likes to handle those for any extended period of time outside of Chansey and the defensive utility it proves as a Hydreigon switch-in is great.
C -> B
Why did we drop this again? We're not acting like Scizor is some death knell right? It can't switch into this thing reliably at all and Chansey usage is extremely down too.
vivalospride has been fiending the ladder with a Specs Vanilluxe team that shows how lethal this mon still is. It shouldn't have dropped imo.
A- -> B+
Tenta hasn't really gotten worse. It's just been ranked too high for a pretty long time. Doesn't really check anything specifically except for Prim which is admittedly nice but not enough for a slot in A-, and while it's def annoying to switch into I don't think it's really on par with mons like Swampert or Rotom-W as evidenced by its low usage. B+ fits it way better.
B -> C+
Honestly it just sucks outside of HO and is hard to fit even on HO. Doesn't deserve to be ranked alongside or even above HO staples like Cloyster and Froslass in my opinion.
UR -> S
UR -> S-
A -> A+
A -> A+
A- -> A
A- -> A
A- -> A
A -> A-
B+ -> A-
B+ -> A-
B -> B+
B- -> B
B- -> B
B- > B
C+ -> B+
C+ -> B-
C+ -> B
UR -> B-
UR -> B+
UR -> C+
UR -> C
UR -> C
UR -> C
S- -> A
S- -> A+
A+ -> A
A -> A-
A -> A-
A -> A-
A -> A-
A -> A-
A- -> B+
B+ -> B
B+ -> B
B+ -> B
B- -> C+
B- -> C+
B- -> C+
B- -> C+
B- -> C+
B- -> C+
B- -> C
B- -> C+
C+ -> C
C+ -> C
C -> UR
C -> UR
C -> UR
C -> UR
C -> UR
C -> UR
C -> UR
C -> UR
C -> UR
from UR to C 
's niche in the tier, I think that Sigilyph is a strong alternative as a Calm Mind setup sweeper that more people should consider. As a whole, the UU tier has relatively few users of Calm Mind compared to previous stages of metagame; I personally only see the occasional CM 
, 
much more quickly than Psyshock. Fortunately for Sigilyph, it has no such issue, as it has access to a move that Reuniclus could only dream of: Heat Wave. Psychic + Fire coverage is notoriously strong in the UU tier, with other demons like 
, must be wary of a potential Air Slash or even Dazzling Gleam (another great coverage option Sigi has) before safely switching in.
is amazing for something that wants to stay on the field for multiple turns, OHKOing the aformentioned three at +1 before they can retaliate.
or 
, it is far from unusably frail, being able to survive nearly all relevant priority moves from full, and tanking most SE special hits at +1. Its speed tier also makes it less susceptible to FuturePort than those slower setup sweepers, as 
