I like how they seemed to have made both you and the aliens significantly more powerful and mobile. One of the main problems with Enemy Within is that Firaxis had trouble balancing the lategame when you're fielding full squads of gene-modded or MEC soldiers with plasma gear, which meant they had to do really cheap shit like give the Sectopod %50 damage resist to prevent you from steamrolling everything.
Though I do wonder how much the lategame differs from the 3 month preview build Firaxis released. Hopefully they didn't spoil too much of the game, but I sense they've still got some surprises in hand.
Seconding that. I could never get into classic X-Com's UI or its fiddlier bits (having to purchase ammo manally) but Xenonauts does a great job streamlining the extraneous bits while retaining the more tense, tactical style of the game.
It also has a much more involved strategic game, which XCOM 2 sounds like it's emulating in some ways -- aliens complete research missions, establish bases, and mount strikes against your bases in retaliation for shooting down their UFOs.