The poor gameplay balancing and grind-tastic gameplay, mostly. The former made the latter even worse. The game seems to derive NPC stats from your own, which on top of defeating the purpose of leveling up almost as brilliantly as FF8's "enemies level with you" system does, also makes it so that some absolutely ridiculous things can happen. Like, say, sending a horse running off at mach 5 when you hit it because your Speed stat's maxed. With all the grinding you have to do to get your abilities up to par, the fact that your enemies all end up exactly as abled as you just adds a whole new layer of insult.
Oh, and I really don't like how almost every mission boils down to one choice, that choice almost always being either "kill somebody and collect proof of their death" or "steal something and don't get caught".
Sky Render - Sanity is for the weak.
