I don't want to comment much because it's not yet playable, but I do want to point out a few mons that I think will be fun and solid. I also want to defend the decision to start Terapagos OU, since I've seen a lot of people complaining about it.
I think it's wrong to at least not try Terapagos, even if it lasts 3 hours. We know BST isn't a good enough argument to ban something especially in a situation where we're still not 100% sure how well Terapagos's weird mechanics will play out in a singles setting. I'm fairly certain the Stellar form will be broken. I believe it should be precedent to allow pretty much every new pokemon to start OU unless it is very obviously broken (Koraidon, Miraidon, etc.) In theory yes, it's absolutely busted, but especially with the wack mechanics of this DLC and specifically this mon, no reason it shouldn't be tried in OU. Also, I think the new tera type will be almost zero used on anything other than Terapagos, and contrary users like Serperior and Enamorus. It's bad.
Weather will be bad to start IMO & so will Gouging Fire (also known as Packing Heat). Terapagos is going to be spammed and the Stellar form getting rid of weather is going to impact Gouging Fire negatively, unfortunately. I do believe this mon will be a healthy offensive presence in the meta, because it has a number of offensive & defensive counterplay, and is held back by the recoil in order to have good fire STAB. It's also going to want to run Loaded Dice to boost Scale Shot, but it also really wants Boots. Looking forward to this mon if Terapagos ends up being too much
The Cons of Iron Crown: bad typing, mid speed tier, outclassed by a lot of other booster mons
The Pros of Iron Crown: it's going to win a lot of games regardless
this thing is going to be mad broken, book it now. no explanation to why, it's just going to be good. great movepool and great bulk and will be a great defensive tera user & sweeper.
wait... wait....
we did it boys, BW sand is back in a big way.