When using this theme, no matter the kernel version, hardware, arhitecture (32b, 64b) or gtk version, most apps using gtk are very slow and sluggish. Example of apps: - synaptic - bluefish - bluefish-unstable - geany - gimp Most GTK apps that use tabs or have icons in them are sluggish, and for bluefish-unstable and geany, the more tabs you open, the more sluggish they get.
Looks like this theme just not a very good performer. You can use GtkPerf to compare performance and UI responsiveness of various themes: http://gtkperf.sourceforge.net/index.php?page=testing&id=1