When I upgraded from Squeeze to Wheezy, the Gnome desktop tried to load, flickered, then switched to "classic." There was a notification balloon to tell me why, but it was positioned partly off-screen so I'm still none the wiser. So I didn't get to try Gnome's Hell (or however it's supposed to be typed), but the "classic" is anything but a classic.
Thankfully I found a bug-fix: XFCE is fast, stable and extremely customisable - a lot like Gnome was ten years ago in fact!
All I had to do then was replace GDM3 with GDM2 (which was a lot easier than I'd thought), reinstate 3-button emulation in X.org, and the desktop was as good as it was in Squeeze!
This raises a question: How many of the recent changes in the big Linux desktops were actually proposed by Microsoft moles?