Even themes advertised as Gnome-shell 3.4 compatible have graphical issues on Gnome-Shell 3.4. The main thing is that the text is black and nearly invisible, and the icons in the applications screen are crowded and in some cases overlapping. The themes did not do this before upgrade, and the default doesn't do it now. I am using user theme extension, and the themes I have tried are the Ambiance-Color set and London Smoke (both of which are advertised as 3.4 compatible).
Here is the right way to get gnome-tweak-tool (advanced settings) to work therefore shell themes and extensions to work WITHOUT breaking your gnome shell
sudo add-apt-repository ppa:ricotz/testing sudo apt-get install ppa-purge sudo apt-get update sudo apt-get install gnome-shell-extensions sudo apt-get install gnome-shell-extensions-common sudo ppa-purge ppa:ricotz/testing (type N and press enter at the end of the process)
Restart the shell (Alt F2 >> r >> enter)
Most of Gnome Shell themes are currently incompatible with Gnome 3.4, the same for some extensions. You can look for updated themes on Deviantart for instance.
I'm currently using this theme which works pretty well. http://www.ubuntuvibes.com/2012/04/orion-gtk3-and-gnome-shell-elegance.html
Furthermore, first delete older themes in .themes directory before installing the new one, otherwise, it won't work.