What we know about USUM

New Pokemon:

Dawn Wings and Dusk Mane Necrozma
    -Necrozma by species
    -Retain Solagelo/Lunala Typing
    -New Exclusive Z-Move:
        -Menacing Moonraze Maelstrom for Lunala
        -Searing Sunraze Smash for Solgaleo
        -These will go off of their signature move (sunsteel strike or moongeist beam)
Dusk Form Lycanroc
    -Event exclusive, evolve event rockruff between 5 and 6pm
    -New Lycanroc Z-move: Splintered Stormshards

UB-Assembly
    -Rock/Steel type
    -While unconfirmed, most likely a tank.
    -Known moves: Iron Defense and Wide Guard
UB-Adhesive
    -Poison type
    -Known moves: none
    -Pokemon that comes from the same Ultra Space as the URS (most likely)
UB-Burst
    -Fire/Ghost type
    -New exclusive move: Mind Blown

Other New Moves:

Kommo-o
    -Clangourous Soulblaze (Z)
        -Deals damage to all targets and gives an omniboost

Necrozma
    -Photon Gyser
        -Measures attk and sp. attk and does damage based on the higher stat

Z move also confirmed for Mimikyu and potentially togedemaru

New Overworld Features:

Valley of Pikachu
    -New area full of pikachu and a pikachu inspired RV. A trial guide is visible, likely a new trial.

Big Wave Beach
    -Mostly bare, but noticable is the new ride pokemon Mantine

Mantine
    -New ride pokemon, play a minigame while you surf between islands

Ultra Space
    -Each UB now has it's own area of Ultra Space, that will be traveled to using box legendary as a ride pokemon
    -Currently known locations: https://gyazo.com/a5d1edfa8a8e6e3d08c15ae7e1323a55
    **Ultra Megolopolis**
        -Home of the Ultra Recon Squad (URS)
        -Likely home to end game story elements, necrozma can be seen resting a top a tower in an area very similar
        -Likely has post game elements as there are visible barricades in the trailer
    -In an interview, it was confirmed that there will be worlds full of legendaries, however only mewtwo is confirmed so far

Alola Photo Club
    -Lol who cares

RotoDex
    -Many new rotodex features, including the ability to use two z moves in a battle (story mode only)
    -Gain more features as the game progresses and you use the dex more
    -Shown features: https://gyazo.com/7039b9c65a2d3c947fed5a15e192e2fc

Other:

Alola pokedex confirmed to contain over 400 pokemon, national dex still unconfirmed.