The list of 47 achievements, worth 1,000 Gamerscore, have made it out - for the Games for Windows Live version of Batman: Arkham Asylum. It's hard to imagine these will change much for 360.
Finishing the game on any difficulty (of three settings) returns 50 Gamerscore; 100 percenting it gives you 75, and solving all of the Riddler Challenges (you saw one in the earlier video, looks like a collection item) gives you at least 160, as you're awarded 20 Gamerscore at certain points in your progression (at 5 percent of challenges, 10, 25 percent, etc.) Combo achievements hint at some serious throwdown animations.
There are another 15 secret achievements, three of which are worth 50. The full list is at the link.
Batman: Arkham Asylum Achievement List [Xbox 360 Achievements, thanks again, Excaliburps]