Time to post my thoughts:
Final evolution starters hype! Just like how my opinion on Kommo-o improved after watching gameplay footage of it, my opinion on Incineroar improved after I saw its animations in action. It's still my least favorite of the three starters, but I no longer dislike it. I really like its mannerisms in the way it acts. I'm pretty glad it didn't turn out to be Fire/Fighting.
Decidueye has been growing on me these past few months, but with today's reveal, seeing its animations really made me like the Pokemon. Surprised it turned out to be Grass/Ghost, but that's better typing that Grass/Flying, so I'll take it. I like the aesthetics in its signature move, and it even has a pretty neat effect. Primarina truly looks gorgeous in its 3D animations, already solidifying my love for this Pokemon. I find its signature move interesting in that it removes the Burn condition from foes, but after reading the Pokemon's description, it makes sense.
In all, these starters will probably go down as one of my favorites in all the generations, in terms of the three together. I like Decidueye and Primarina equally with Incineroar being my least favorite, but I can now say I have a favorable opinion on Incineroar.
I'm surprised they revealed the other Tapus this soon. The trailer confirms the GameXplain theory regarding the names of the rest of the islands. I like Tapu Fini the most of the three revealed; now that we have a better look at its design, I gotta say it looks really nice. Tapu Lele follows after it, with Tapu Bulu being my least favorite of the Alola Guardians (the buffed appearance doesn't appeal to me that much). Despite this, Tapu Bulu interests me for the fact it could be the Island Souvenir long hyped about (its Tiki design resembles a human head quite a bit). I really wish we got to see how the other Guardians looked like in their Tiki forms in the trailer. Their Z-move looks pretty cool too, and I can't wait to see how they'll impact the competitive environment thanks to their new abilities.
Not much to say about Cosmog, though I'm interested to learning more about how Aether Foundation has been researching it. Some source yesterday mentioned that Cosmog is the Pokemon was the Pokemon in Lillie's bag. Putting the pieces together, I guess this might imply Lillie really is connected with the Aether Foundation in some way.
And it looks we'll gain access to the Alola Pokemon League in the postgame. I'm betting the Kahunas will turn into the Elite Four, but that's just me.
And the Battle Tree, Cynthia is coming back. That's cool, and so is... hold on... WALLY? WALLY IS COMING BACK! OMG YES! MY FAVORITE RIVAL IS RETURNING! HE STILL HAS HIS GALLADE! YES! YES! YES!
^That was my reaction to Wally's reveal in that trailer. So happy he made a return! Looks like we're going to be dealing with that monstrous Smogon-style team again, complete with that awesome Mega Gallade. He even looks a bit older, but I guess I got that impression from looking at his face. I'm literally going to be playing Wally's theme all day today to celebrate this joyous day. I'm really interested in hearing a Sun/Moon remix of it once I get to battle him.
And Red and Green will return too? Heck yes! I like the new designs on both of them, but I prefer Red's in-game sprite to his official art. You can tell both trainers really grew up. Who wants to bet Red's Pikachu will be even higher-levee than it was in HG/SS?