Things I didn't like..
I thought the shotgun should have spread a little less and therefor been able to kill imps that were a little further away.
The neverending imp-teleporting-behind-you gag. Gotcha! For the 1,700th time! It became routine.. the further I got the more correctly I guessed when they would spawn. Actually, hell, you don't even _need_ to guess. Every battle I got in, I would turn around and backtrack a bit, thinking "Man, they aren't going to do that again, are they?" Sure enough they did.. every time.
Other than that I was very impressed with the game. [And I had high expectations ;)] Sure, it was a little dark, but hey, that's doom3's niche.