I've just installed Fedora 19, to get the Gnome 3.8 goodness. Now I realise that Gnome's animations haven't ever been the smoothest ever, especially when dual screens is a factor.
But now even with just one window in the Overview, it's just painfully jerky when entering the Overview. I'd guess maybe 4 or 5 FPS, rather than the ~6-7 FPS I 'enjoyed' with Fedora 18/Gnome 3.6.
It wouldn't be so bad if this wasn't the core element of Gnome Shell.
For reference, I'm using a pretty cheap ATI graphics card with whatever drivers work out of the box, but even so it's not like I'm running Portal 2 or whatever, I'm just Window Managing - Compiz used to be so much smoother.
Gnome Shell is such a nice DE, it's just a shame the graphics side is a bit sucky.
If anyone has a rationale for why Compiz was much smoother, or why Gnome Shell is pretty jerky I'd love to hear it. And if there's anything I can do to improve it too.