I recently upgraded from 11.04 -> 11.10 -> 12.04.1
Previous to this upgrade this webcam worked beautifully, never slow or choppy. After the upgrade its like watching stop motion.
I have the same issue whether im using Cheese or the google-talkplugin. This does not seem to be related to desktop env im running, all the same Unity, Gnome-panels, Gnome-shell and openbox.
I should not that this machine is relatively powerful, 6cores, 32GB ram and root disk on an SSD. My GPU(im using the latest Nvidia drivers) is not the most up to date but still decent. I am using a Logitech C920 webcam.