Windows 7 Retail Ultimate
Just got my hands on a copy for testing...
I performed a clean install and the O.S. was fully installed and operational in about 20 minutes. Did not need to provide ANY drivers as they were all found during the install.
I have a Quad Core PC with 4GB of ram, I installed the
X64 version and all I can say is GOOD LORD!! Microsoft got this one right. It has the speed of XP and the feel of Vista with a lot of improvements, like the features actually work! If you are like me and tend to have a LOT of windows open you are going to love the new navigation in the task bar. The file libraries are cool too.
All in all, I have to say that I think that this O.S. will be able to compete with the Mac OSX for quality.