If you have an MSDN account you will be able to download Windows 7 Beta today, but it should be available for anyone by the end of next week.
If you have not seen anything about Windows 7 then you should take a look. I am not suggesting that you install it on a production computer, but even early adopters have had very stable installs.
The Windows 7 operating system is to Vista as XP was to Windows 2000. If you look under the covers of these operating system you will find that Windows 2000 was version 5.0 and XP was 5.1. This is the same in Windows 7 with Vista being 6.0 and Windows 7 being 6.1.
And as with windows XP it starts from a stable place, and build from there.
I am still downloading the beta as we speak, but I will do a little blogging on the install and result :)
UPDATE: Windows 7 Beta will be available to the general public from Friday 9th January 2009 (today), but there will only be 2.5 million licences issued.