The minified CSS increased by 5Kb, from 71Kb to 76Kb.
Test page: http://ugomobi.github.com/transitions/
Transitions: Added support for Opera transitions. Fixes #4521.
Looks like all transitions fall back to fade. Have to look into that.
Update: Opera doesn't support 3D transforms. Without the 3D most of the transitions work on Opera desktop, but not smooth except for slide transition. I could only test Opera Mobile on the emulator and transitions still didn't work there.