I have been using Windows 7 since the day that it was released (last fall).
It has performed flawlessly without one problem. I would never go back to the older software. I use a Dell XPS 430. I especially enjoy the new media features of W7.
The built in security along with my add-on security (which seems to update itself every day) has even confused the Google ad guys about who I am.
The system handles the "Re-Spawn" tracking cookies very well.