Xbox 360 campaign demo is available today but with a small restriction on the co-op multiplayer part while the PC and PS3 version should be getting it before the end of the day.
The demo is around 1.7 GB in size and offers 2 single player missions with an extra 2 co-op missions only available now to those who activated their Battlefield 3 Online Pass. Non-pass users have to wait till February 17 to unlock the co-op portion of the demo.
http://www.egmnow.com/articles/news/...demo-now-live/
PS3 PAL version of the demo is reportedly delayed though for an extra day.