Cyber Dimensions....

Windows XP Mode
To encourage enterprise people to let loose and rock Windows 7, it runs a full-fledged Windows XP virtual environment using Microsoft's Virtual PC. It requires an additional download (booo), but you won't have to worry about your applications breaking like with Vista. Update: Paul Thurrott has more info and a huge walkthrough on XP Mode, including the crushing revelation it's gonna be free for Windows 7 Pro, Enterprise and Ultimate, not Home Premium, which is the version regular people are going to be running.

The Most Insane Default Backgrounds Ever
Look at these. Yes, these are just a handful of the ridiculously awesome backgrounds packed inside Windows 7. Some are the products of acid trips through a nightmare land of anime hell that I would never wish on anybody, and some are simply stunning. Just wow. Click to make bigger, obvs. Update: Okay, the backgrounds were in some of the builds between the Public Beta and the upcoming RC, but they weren't, you know, public.