An official Eidos moderator has posted the system requirements for PC version of Batman: Arkham Asylum.
The minimum requirements are:
* CPU: Intel single core 3 Ghz or AMD equivalent
* Memory: XP = 1 GB, Vista = 2GB
* GPU: Shader Model 3 NVidia 6600 or ATI 1300 or higher
While the recommended requirements are:
* CPU: Pentium D 3Ghz or AMD Athlon 64 X2 3800+ (Dual core)
* Memory: XP = 2GB, Vista = 3GB
* GPU: NVidia 7900 GT or higher
Enhanced for multi-core
The PC version will have achievements too, and will come under the Games for Windows branding.