I was really surprised by all the negativity on the Total War Forums. I had played the game for about 8 hours on easy (with rome) just to get the hang on the new system before I started a harder game with a harder faction. I went over to the forums to see what factions people liked the best and saw 90% of the threads were proclaiming the death of the franchise and the betrayal of the fanbase. Yeesh. Maybe I'm just lucky, but I've had zero performance issues (with a slightly above average pc), and no bugs at all (that I've noticed anyway). I really like the way battles feel; a large army marching feels and sounds like a large army marching, and after orders have been issued and a large melee is underway, I like to drop into cinematic view and enjoy the spectacle for a moment or two.
I've heard a lot of complaints about the new interface, and I think they are mostly unwarranted. It looks simplified, but all the information you'd expect is still there, it's just either a click or two away, or requires you to mouse over an icon. This may slow you down a few seconds, but as a result the main screen is much less cluttered, which I think is an acceptable compromise (YMMV).
There were only two things I was really annoyed by (so far anyway).
1. Why the hell are there control points in open battles? I started a battle on a map against a larger force, and deployed some troops in a forest with the intent of using my skirmishers to lure their force into an ambush. All well and good, but suddenly, after their troops had advanced a bit I lost the battle. Before any troops had engaged. What? So I checked the replay, and then noticed a random circle on the grass somewhere near the middle of the map that the enemy army walked over for about 15 seconds, and then "captured" (how you "capture" a circle of grass is beyond me). That feature needs to go away, but I'm pretty sure a mod will give the option to remove those... or at least I hope so.
2. No one (meaning any of the AI) wants to fight open battles! That example I listed above was such a surprise... because it was the only battle I engaged in (non-naval) that didn't take place in a city. Maybe it was just because I was on easy (yes, yes, I'll get to a harder difficulty soon, shut up) but the AI armies did exactly two things. Defended their settlement, or went directly to my settlements to try and capture them. I much prefer open battles (lots more options) so this is very disappointing. Again, it could just be because I was playing on easy. I'm about to start a game on hard as Parthia, so we'll see what happens.
Anyway, despite a few annoying little niggles, I really like Total War: Rome 2 so far, and was really surprised by all the hate!