Woohoo! The nicest thing about the updated Comcast DVR software is that 30-second skip works!
I had "hacked" my remote a while back and reprogrammed one button we never use to send the command to jump ahead 30 seconds . (If you're looking for info on how to do this yourself, go here.)
With the old DVR software, hitting the button would just bring up a "not supported" message - but the new software happily jumps ahead. Not quite up to the level of my old ReplayTV unit (which would skip adverts automatically), but I'm quit happy.