Expect a few new alola forms, but not so many. Some are Vileplume (psychic/poison), Bellossom (psychic/fire), Kingler (water/steel) and Stantler (normal/ghost)
At least 2 more new UBs not revealed (one is dark/fairy)
Old villains are a pain in the ass to defeat, they all use legendaries in their teams. In US Ho-Oh, Groudon, Dialga, Reshiram and Xerneas, in UM the opposite pokemon
You can only catch the opposite pokemon in each game (Lugia in US, Ho-Oh in UM for example) through the wormholes
EVERY pokemon from older games are catchable, mythicals included
The post game is decent, even the pickiest gamers will enjoy

Also, don't screencap this or anything. These are all lies :^)