One feature that will make plain old Revit users a bit miffed is the new perspective view mode that you can model and see your model in perspective at the same time! Yeah, I know...like who wants that? (that's sarcasm if you are Sheldon Cooper btw)
It's been updated at Autodesk Labs now, you can go there to download it. They extended the update to expire on August 31, 2012. Keep in mind that the site says the program will no longer operate after that date.
Check out the videos at You Tube, I embedded this one as the temptress, be tempted you know you want to be.
Video - Overview
Video - Extruding Faces