It was all over the place. Even if it didn't go below 30 it was still jarring.
To be honest I never felt it to be jarring because the motion blur helped eliminate the effect of variable FPS. But you are right that it was all over the place and particularly in the really epic moments like the opening sequence which I assume was really resource intensive. I think Digital foundry had a video of the frame rate analysis that they did for the opening. Here it is - http://www.youtube.com/watch?v=woad5I3hYOc
Really jumps but I never felt it somehow.