For one, it's terribly short according to them! I dunno, I've heard 20-25 hours on your first playthrough which is pretty much the standard time for an RPG-like game, summary: I think they are twats on this statement. The second statement is that the framerate sucks as well, but again, almost all games these days show signs of lag every now and then, and as long as it's not waiting around the corner for every 1 minute, I honestly don't care. The third statement is that the AI sucks (remind me where a RPG actually had an impressive AI where they would actually just hit you in the head with a sword rather than waiting for you to do your attacks and blast them into an oblivion).
Unfortunatly most of that is true.
If you don't do any side quests then the game is VERY short. I'd say with no side quests/extra a first playthrough would last 12-15 or so hours. If you know what you're doing it would be easy to half that time. But there is a fair amount of extras and side quests, so if you include those then the length of the game is fairly long. Add to that you can play as different classes and be good or evil and it gives the game a fair amount of replayability (if you ask me, being evil is a how lot more awesome than being good, which is boring).
As for framerate drops. It isn't as bad as people make out. It does happen, and it can make the game unplayable while it is happening, but it rarely happens.
But the AI... Ugh. Enemies can pretty much see you from anywhere on a level, and have 100% accuracy even from the other side of a planet (obviously you can't even see them). But other than that the enemy AI isn't too bad. However... Ally AI is terrible. They will constantly get in your way and jump infront of your bullets, or they will try to shoot through you. The problem with this is that you cannot shoot through an ally and they can't shoot through you because shields block the bullets. That and they like to inappropriately use skills and abilities (such as using a skill that drains shields on an enemy with no shields). And a problem I've had is that they tend to like changing weapons... To weapons they have absolutely no training in, which makes them totally useless until you've forced them to change their weapons back. But I didn't find allies to be too useful later on in the game, I'd more or less end up using them as meat shields while I picked off enemies with a sniper rifle (which will 1 hit kill more or less anything later on in the game).
But yeah. The only one of those that really annoys me is when allies jump infront of bullets (or sometimes grenades... Oh how fun it is to commit accidental suicide with a grenade!). The others don't have that much of an impact on the game at all (if you play through twice, one good and one evil and do everything you should be able to get at least 50-60 hours of gameplay out of it, and the slowdowns tend to only happen at the start of an area).