I ended up missing all the TotSC stuff when I played a couple weeks ago. Supposedly Durlag's Tower is a huge pain in the ass, but also the best dungeon in the series. I ended up running away when I got my butt handed to me by the battle horrors outside the tower.
Watchers Keep is better, much better.
I didn't like Watchers Keep. Too boring.
Durlag's Tower was the best part of the original BG. I'm not really into puzzles and riddles but the developers did a fine job with Durlags.