Fantastic pacing, awesome realization
What more can be said about Batman: Arkham Asylum that hasn't already been written. Excellent combat, great pacing, a good story in the Batman universe and just an overall fun experience. It goes without saying that this game is easy to recommend but I would extend this to say that if you like games such as God of War or Star Wars: The Force Unleashed you'll love Arkham Asylum.
In particular the detective elements of solving Riddler challenges adds some depth and fun to the main story and combat. It's rewarding and fun in its own right. The game allows you to enjoy every element the developers included without any one piece getting in the way of any other.
This will be a game you'll play through and will be entertained right through to the end.
Bottom line verdict: Get it.