As a long time user of Gnome 2.x, I welcome most of the changes made in Gnome Shell, haven't had any worthwhile complaints since the 3.4 release. It's cleaner, faster, has better window management features, and just gets out of the way better than Gnome 2.x ever did.
Totally agree with you. I didn't like the gnome-shell when it first came out (slow, buggy as ...), but I like it now: it's very clean, does what I need with little effort, and stays out of the way otherwise.
I wish there were more themes around though ... it seemed like themes were plentiful and easily usable in Gnome 2 but they seem kinda thin on the ground with Gnome 3.
[I gather the WM in Gnome 3 is compatible with Gnome 2 themes, but GTK 3 cannot use GTK 2 themes ... or something. I dunno. The multitude of theme formats is confusing.]
The real key is find Gtk themes that are compatible with both the Gtk2 and Gtk3 engines. Combine that with a good Gnome-Shell theme and a good font, and things actually look really nice.
I actually just found a couple new themes that are really great:
