I upgraded my desktop yesterday to Debian 'Jessie' 8.0. Can't say it went smoothly. First of all, lot of packages got deleted; no biggie there, easily reinstalled. However, the kernel didn't got upgraded, which caused quite some problems during first boot. The worst part however, was that I was using an incompatible Gnome theme. This did cause segfaults of many Gnome applications, such as gnome-terminal. Quite strange that Gnome cannot catch those kind of exceptions. I would expect that Gnome would revert to a default theme in those cases.
It took a while to find the cause of that (adding a new user and charging up a desktop succeeded fine, so I knew this was a user config error); in the end, the next couple of lines fixed all of my issues :
$ gsettings set org.gnome.desktop.interface gtk-theme Ambiance
$ gsettings set org.gnome.desktop.wm.preferences theme Radiance
Shame that Gnome 3 is so ugly. Why all that grey-black,and those rounded message boxes ? I really miss the days of Gnome 2's default look and the Ubuntu Netbook Remix interface...