Gnome Shell caused me to switch from Fedora to Debian (stable). I liked the design decision of focusing on keyboard input. I've always wanted a desktop environment that had the efficiency of Vim, and Gnome Shell is a step closer to that. However, it was buggy as hell on both my machines; crashing about every day on my notebook, and about every hour on my desktop. This was a little over a year ago, so it may be less buggy now. But, I'll just wait until Debian Wheezy becomes stable to make the switch.