The above bug seems to be solved or at least mitigated a bit. With just having firefox up the CPU usage of gnome-shell is between 2-5%.
Gnome shell is still much less performant than Unity though, by moving windows, open Activities or dragging the mouse over the dock its CPU usage quickly jumps to 20%. But that is probably things that should have their own bugs.
The above bug seems to be solved or at least mitigated a bit. With just having firefox up the CPU usage of gnome-shell is between 2-5%.
Gnome shell is still much less performant than Unity though, by moving windows, open Activities or dragging the mouse over the dock its CPU usage quickly jumps to 20%. But that is probably things that should have their own bugs.