Metagame is pretty fun right now, but I'm sure some bans will be needed. There are a few mons that I expect to go back to OU by usage, as well.
First, the formerly UUBL pokemon:
I'm really enjoying Iron Hands, but he should probably go back to BL (unfortunate, since Tusk invalidates him in OU). It was banworthy before, and not much changed. Skeledirge kind of checks it, but not entirely, and it has a good matchup against almost all of the other Home pokemon that dropped this month. Best check is probably still Quagsire, and that didn't stop it from being banned the first time around.
Hydreigon will probably end up back in BL. Not as clear cut as Hands, but not too much has changed here. Tera steel+sub+nasty plot still smokes most of the tier. Other than general power creep, it hasn't really gained any significant counters from the drops.
Unlike the other two, Iron Leaves might now be fine for the tier. UU gained a ton of mons that create problems for Iron Leaves, and stop it from being oppressive with the booster energy (speed)+swords dance set. UU gained a lot of flying types, which Leaves doesn't like. Skeledirge can wall it, depending on the set. Scarf Meow can beat it. Leaves is now extremely reliant on having the right 3rd move for coverage, and is forced to tera more often than not. I almost never see this pokemon, right now. That said, if other bans go through, it might become a big threat again. For now, very manageable.
For new pokemon:
Not too much to add here. It is very good. Maybe too good. Works as both a wall and a win con. In UU, It doesn't face the same pressure that it did in OU, and it was still a good mon in that tier. It might be banworthy, and it also might rise back to OU by usage at some point.
Maybe banworthy, but I don't think it is going to stick around in UU for long enough to find out. This was the first mon to miss the OU usage cut (was at 4.2%) in June, and I think it will get back above 4.5% usage at some point. It was the 9th most used pokemon in OU in May, and while it did gain counters and competition, it still should be quite useful in that tier after an adjustment period. Anyway, while it is in UU, it might be the best pokemon in the tier. It is the second fastest mon, behind Talonflame (tied with
Noivern, which I haven't seen post drop), and can run a number of viable sets. Scarf, Band, lead/sash, etc. all work very well, which makes it hard to predict. Personally, I like scarf+trick. Meow outspeeds most teams without scarf, so it can get rid of the scarf and cripple an opposing pokemon if it is facing a slower team. Flower trick, knock off, and u turn are all extremely spammable moves. It can get up spikes if needed. Really great all around.
Beyond that, there are a bunch of really interesting drops, some of which might be banworthy.
Arcanine-H is great. Very few switchins to choice band and tera normal espeed is a good win con.
Thundurus-T is powerful and is able to take advantage of the lower speed tier in UU.
Moltres-G can become a really good wincon in the right conditions (usually behind screens + tera fairy).
Zapdos-G is a great choice item users.
Enamorus-T seems unexplored. The setup sets work well, but I think it could be effective with a simple specs set that takes advantage of the strongest moonblast in the tier.
Basculegion-F is almost as hard to switch into as Arcanine.
Breloom could become a top tier threat after a few other bans. I'm not as sure about
Tornadus-T, which should be great in theory, but is really missing its utility moves (relying on low accuracy moves also hurts).
Plenty of pre-home UU mons are still good, as well.
Donphan has been mentioned, but
Hippowdon is also very useful right now. It beats many of the new physical threats (especially with rocky helmet), phases out setup mons, and puts up rocks.
Talonflame is still good, specifically in a utility role. Defog+taunt+flame body can put in a ton of support work.
Scizor, obviously, is still good.
Tinkaton remains a staple, especially with encore. Last, but not least,
Forretress remains the premier UU pokemon, essential to any team.