At first my main problems with the gnome-shell were basically about usability. I found it (and still do) to be much worse than gnome2, but I could somehow even leave it on my desktop as a secondary choice if those were the only problems. Then I noticed how orrendously bad it performs, in particular for my case, that is someone who leaves many windows open all the time (like 100 windows of a browser like chromium). I couldn't use the system at all anymore, so I completely removed gnome from my system! Unfortunately currently xfce is buggy on debian unstable+experimental (like the window manager doesn't work, I don't know, I just noticed that the maintainer thought it was a good idea to close the bug report about this(reported by someone else)), so I'm currently using KDE. Without the semantic-blablabla which eats your cpu and hd space, it isn't bad!