I'm on 3.8 in Fedora 19 and my overall impression is it's pretty fast & clean.

Haven't had much luck getting gnome-shell-extensions running well. I got the weather one going by taking the one from the gnome site rather than the rpmforge package but system monitor, pomodoro timer and a couple of others aren't playing ball for me currently.

I have had to google how to do a bunch of different things since switching to it. I still don't know any commands except restart for the snazzy alt+f2 command overlay.

I'd most like it to add a apple key+space style search from the mac world.

Most interesting new app there is "boxes", a virtual machine / remote machine viewer / manager mashup thing. Looks quite promising to me.