e17 is not released yet no. Personally on my install I havent had any problems yet doing audio work. As was said above the mouse hangs for half a second when it hasnt been used in a LONG time, but I thought that was a problem with my wireless and NOT e17 myself
I havent had anything crash yet, any real hiccups or bugs myself, though I havent customized it yet like I really should. The aforementioned ALT problem is probably due to e catching the alt and not sending it to the program(At least when you rightclick, that always pulls up the e menu, very handy at times but I havent started using blender yet so I will probably have similar problems, then I will look into it more), I am sure there is a fix for it I dont know yet though
Fluxbox aint the prettiest thing out there by any stretch of the imagination, but it is fast and works. Gnome can be decently fast and work, and well its gnome, I am sure everyone here has seen gnome at one point or another
Xfce I wasnt to impressed with when I tried it to be honest. But that is just my opinion, take it with a grain of salt.