Right off of the bat gonna chuck out a few observations based on my (admittedly limited) time on the suspect ladder and in the Medichamite meta:
Rapid Spin: With Pheromosa gone from the tier, hazard control on offense is in a bit of a dismal state. All defoggers blow chunks, all spinners blow chunks. However, the departure of Pheromosa has opened up a small niche for Starmie in that it is now the only fast, un-scarfed spinner in the game that isn't completely unviable (see: Cryogonal) and there are no viable spinblockers. In a meta where Spikes is completely busted due to lacking hazard control options, noone really preps for Starmie spinning by bringing Jellicent and, as such, there isn't really anything viable that stops it doing so. It just generally is nice for role compression, although Greninja/Koko existing are huge headaches for it.
Mega Medicham and Alolan Marowak: As expected, Mega Medicham is completely nuts. Having the single strongest attack in the game in HJK does wonders for this Pokemon's ability to really tear defensive Pokemon apart, and with the introduction of terrains allowing it to circumvent some of its biggest headaches, it really is just really, really, threatening. Speaking of double Atk stat nukes, I saw
Ema Skye mentioning that Alolan Wak is taking a huge hit from the lost of Pheromosa, but on the Pheroless ladder I found that it was still one of the most useful Pokemon in team building because of the way that it keeps a lot of extremely useful stuff in check (don't undersell how important discouraging the use of TBolt/blocking Volt Switch w/o being weak to HP Ice/neutral to Gleam is for offense), and furthermore with the introduction of Mega Medicham it is able to stop it mindlessly spamming HJK whilst completely shutting down BoltBeam+Fake Out sets with no repercussions at all if it carries Lightning Rod. FerroWak still completely dumps on teams even when they carry Mag due to Ferro being able to double into Wak right as Mag comes in for a free kill (seriously, people never realise how weak their teams are to Wak until they get steamrolled by it). Non-Pyuku stall also still has a grand total of 0 answers for it--especially if it carries Rock Head and, as such, doesn't need to fish for Def drops to take down PhysDef Unaware Clefable if it gets a free switch--and honestly I can't see Alolan Marowak ever doing anything other than hovering at around A-/B+ just because I can't see it ever realistically not having that level of utility.
Both Greninjas: Fuck both of these Pokemon. When building offense I'm finding myself feeling unfairly pigoenholed into an extremely small pool of Pokemon in order to not be steamrolled by either of these, and it is incredibly frustrating because it means that all of my builds look fucking identical. I don't want to have to carry one of AV Tang, Tapu Fini or Primarina to not get steamrolled by Ash Greninja, and as such I just find the way it pigoenholes me into stuff like this to be incredibly unhealthy. And we all know the deal with Protean Greninja; if you don't have Ferro or Toxapex you're gonna have an extremely hard time stopping this thing just coming out and getting a kill or crippling something every time, and given that HP Fire is everywhere now you can't even fall back on Ferro all that consistently and have to really go out of your way to play around it. To add insult to injury, Spikes has little-to-no counter-play anymore and both of them click Spikes without really losing much by doing so. I don't like either of these at all.
Mega Metagross: If you don't want this thing banned, you also want to watch the meta be stale for the rest of the generation. This may sound like me being harsh on the anti-banners, but the way that this thing restricts building is one of the biggest reasons why building in SM OU fucking blows, and there is little--if any--counter argument for this, and it just needs to fucking go imho.
Spikes: Due to the dismal state of hazard control in this meta, Spikes is just incredibly stupid to deal with. Greninja and Ferrothorn spike on quite literally the whole meta, and it just means that a lot of teams find themselves getting overwhelmed by it while also turning a lot of games into who can get their Spikes up first; Spike wars between Ferrothorns aren't an uncommon sight at all, and it is just incredibly nuts to deal with on the whole.
Rotom-W: Rotom-W comes across as anti-meta to me. There is very little really in terms of 'mons that can stop it Volt Switching on the meta due to all of them either dropping to Hydro or being crippled by Wisp, and as such it just poses a very large threat to a lot of offensive teams without them really realising it, and its immunity to Spikes means that you can't even punish it with stacking. Preparing for this in the traditional sense is honestly just harder than ever because Volt Switch really fucks with the concept of checking Electric-types with resistances. I'm interested to see whether this things usage increases, because honestly like Rotom-W is one of the most infuriating things to deal with atm.