@Bas: It's not one of those "yet another" projects, it is an open source implementation of the XNA framework, one-to-one. Plus it is more (ie multi-platform).
Yes it is easy to port over. I ported the game that I demo with to students in minutes. My team and I are porting one of our Windows Phone games with changes only to adopt to Windows 8. Nothing unexpected.
Only thing missing right now is the out of the box content pipeline support, which should be right around the corner (if not already since the last time I checked).