I voted for AI, though.. none of those things really suck. I've gotten too used to 2.5 ui and haven't yet tried out the new one so can't comment on that, same thing with ugvs - they haven't been around and this is how I've gotten used to playing this game... though I do remember missing them when I first played, with xcom 1 in my mind.
AI doesn't seem as bad now as it was a couple versions ago, especially with the increased difficulty (which has an impact, when it was easier the stupidity was underscored) . I played a lot of missions yesterday and thought of this with fear, when or if someone comes up with a proper AI capable of realizing that a puff of smoke is hiding my entire squad I'd be lucky to win one mission in this game =)