You may or may not have heard that Windows 7 Beta 1 was made available to the general public on Friday, January 9. It's getting a lot of good reviews so far from the press and the blogsphere. Aside from the smaller resource footprint, faster boot time, and the ability to connect your work machine to your home network to utilize its resources which was talked about at the PDC in October, I don't know much else (yet). For the developer community, a lot of videos have been made available on Channel 9 covering topics like how to designing the Windows 7 Task Bar, a look inside Windows with Mark Russinovich, and more.
If you want to try out the beta, as with all beta OSes and products, don't use your primary machine if you can avoid it. Either use a spare machine, create a dual boot partition, or use a virtual machine like Microsoft Virtual PC 2007.
Brian Keller, one of technical evangelists and host of Channel 9's 10-4, wrote a great article on how to install Windows 7 Beta 1 onto a VPC.
Definitely a lot of good things are coming in this release. Stay tuned!