Yes, I have installed Windows 7 Ultimate version. It took just 20 minutes I believe. I went for custom installation and having two OS - XP and W7 at present. The major migration to W7 has been done but still, I need to install some more software.
Good things I felt about W7 :
1) Resource utilization mechanism between various process. It is fast.
2) Driver updates are more user friendly now.
3) Windows media center. It just rocks & I did find it effective compared to normal WMP 12.
4) I personally liked that 'No Grouping ' in task bar.
5) Auto updates from Microsoft. :banana2 I liked this in XP too.
Things which annoyed me
1) Too much of security.
Same as Vista I believe.
2) Run as Admin option is necessary for most of the things. I did not like this, because once you have logged in as admin, why there should be a separate option is expected to run as admin?
I am yet to run the Java/C editors & servers in this. If it is not compatible like in XP, I will try that official Virtual XP environment patch for W7. If it is giving problem still, probably I need to stick back to XP. :sarcasm