First up, let me say, that this game does have some substantial improvements from the original. The added prestige classes, the varied upgrades for armour, weapons, and lightsabers, and the individual agenda each party character has, rather than the "peer pressure" exhibited by the party members in the first game.
Now the bad news, ignoring some of the glitches and choppy frame rates, which to be honest are minimal after you add the patches, it is painfully obvious still that KOTOR 2 was an incomplete game. The storylines are very indepth and they do get you involved, but this only leads to a bigger fall when the game fails to deliver. The endings, or lack thereof, were by far the biggest disappointment, especially if you played out both endings of the first game. Secondly, there are quests which you don't get to take part in, even though they are mentioned to you, the most obvious being the HK-50 factory, which is a great shame because the idea of HK-47 going genocidal on his "cheap copies" was a big hope of mine when the quest was first introduced.
Another disappointment as was mentioned in another amazon review, was the confrontation of the big baddies. For me, confronting Darth Nihilus, (The scary guy with the white mask on the cover of the game) was a big let down. Darth "I sleep with vibroblades" Sion, wasn't a great confrontation either, although I can see where the developer's were going with that one. So I can't really complain too much.
All in all however, this game will provide you with days of gameplay. Bearing in mind it takes about 20 hours to finish the game on one path. If you consider you can be light or dark, and there are 3 prestige classes, as well as 3 starting classes, like wise for added difficulty, you can attempt to stay neautral throughout the game (a path I haven't tried yet), you have the makings of a game that you can keep coming back to. Also the addition of being able to turn your party members into Jedi, is a welcome change and a nice touch.
If you are a fan of the original or Star Wars in general, you will be happy with this game despite it's failings and I would certainly not try to disuade anyone from buying it. Just don't build your hopes up for the ending.