At CES 2009 in Las Vegas, Steve Ballmer just announced the general availability of beta versions of Windows 7 and Windows Server 2008 R2!
Windows 7
I've been using Windows 7 on my main work desktop and laptop for a while now; the experience has been amazing, especially for a pre-release operating system, and I'm thrilled that customers can now evaluate the OS. You can find more information on Windows 7 at http://www.microsoft.com/windows/windows-7/default.aspx. I also highly recommend the Windows Team Blog, and the Windows 7 Engineering Blog.
Windows Server 2008 R2
Cooler still for an old server admin like myself is Windows Server 2008 R2, Microsoft's first 64-bit-only OS. Server 2008 R2 features tons of improvements and new features, from better performance on modern CPUs to enhancements in Hyper-V, PowerShell, VPN, and Remote Desktop. Find out more about Windows Server 2008 R2 here, or on the Windows Server Division Weblog.
Windows 7 and Windows Server 2008 R2: Better Together
The coolest story of them all takes place when you use Windows 7 and Windows Server 2008 R2 together... I'm particularly pumped about the new remote workplace solutions! You can find out more about these features here.