One is a psuedo commercial-skip where one of the remote's buttons gets remapped to skip ahead 30 seconds (the length of most commercials).

I have Dish Network's PVR and it has skip ahead and skip back buttons. The skip ahead moves forward something like thirty seconds and the skip back moves back about 10. Thus you skip agead, skip ahead, skip ahead, skip ahead, see your show, and then skip back, skip back. This works great letting you bypass the commercials in only a couple of seconds.