well, considering the amount of time they spent developing the game, i think they managed to pull it off quite nicely. the environments could use some more graphical detail, and to be frank, the graphics just aren't very impressive.
the gameplay has gotten a bit more complex with some new feats and stuff, but there's nothing overwhelming about it. the only thing i wish is that there would be some consistancy with the difficulty. some area's are filled with baddies that are so difficult, i had to restart several times. then, in other areas that are supposed to be extraordinarily difficult are overwhelmingly easy. i just don't get it....
the sound is impressive, and it has a nice musical score, but sometimes, the music can just suddenly become loud and out of place.
the best part (so far) is the way the storytelling is. its nice to discover things that are happening to your character, but it makes for a more cinematic feel when you see something happening that your pc has no clue about. i just happen to like that better.
overall, i think kotor 1 had a bit more polish around the edges, but TSL is still one of the best rpg's i've ever played.