I bought IU at release and kinda forgot about it for a while even though I was really anticipating it (I guess the negative impressions did that). But I finally started playing and I'm about 6 hours in and loving it so far. Up until Nolaan te game is pretty iffy, the random gameplay elements that you're forced to play just aren't fun, but at Nolaan the game really takes off imo.
I've heard people say the environments are barren and too big, but I guess they must be the same people that hate FFXII for the same reason. I personally love huge environments. These aren't as involving as FFXII's but they're fine so far (I'm about to go to the desert, so this could still turn out badly, who knows).
The battlesystem is a bit clunky but very manageable, the framerate seems stable to me and the voiceovers are not great, but also very acceptable.
I just don't see what's wrong with the game. Unless it really goes belly-up during the latter parts of the game, I think this could be the best jrpg on the 360 so far (that's not saying all that much, I know).