My personal problem with Gnome 3 besides the Gnome devs attitude problems, is the technical design of the Shell.
I'm no developer, but the design of Shell, and Unity for that matter, concern me. Correct me if I'm wrong, but it seems Unity is essentially a plugin for Compiz and Gnome-Shell is probably similar in it's dependance on Mutter. Basically these environments are dependant and tied into the compositer/WM and not modular.
If something in the window manager crashes, the whole environment can go down (I'm sure we're all familiar with the 'Oh no! Something went wrong' messages).
I guess they are trying to create tightly integrated environments yet it still seems odd. KDE, XFCE or E17 for example, can switch their compositors on and off (that in itself is handy) and don't rely on 3D acceleration. You still get the same desktop either way.
And now Unity and Shell are trying to push non 3D users through software rendering and boy, that seems pretty slow and horrible.
I think the Elementary team, despite being such a tight and integrated experience, have the right idea. I'm not sure about the need for 3D yet, but parts of the desktop like Wingpanel (the main panel), Plank (the dock) and even the menu (Slingshot) are modular and can be replaced if you wish it.
<sarcasm> How dare you to question the gnome shell vision? You are obviously a hater. Go away! </sarcasm>