[City of Villains] That villain planner I linked before seems to be unavailable, so the quick version of “everything you want to know” is here (well written). At least, that’s everything I wanted to know, except specific powers. You can find specific powers elsewhere, in a lot of places, if you’re that interested. Yes, A LOT of them repeat COH powers, so you’ll mostly be interested in the new ones, which mostly means Mastermind primaries. (You get three summon powers that can all be active at once, some minion buffs, and some attacks).
The very quick summary? “There’s lots of really cool stuff, so if you’re a COH player who isn’t so upset about Enhancement Diversity that you’re planning to hate Cryptic forever, you’ll want to buy this.” Not that there’s anything wrong with either choice.