One of the things I didn't like about the Comcast DVR is that after fast forwarding you didn't automatically go back a few seconds when you pressed play. After hitting play I would press the instant replay button to go back a few seconds.
Then it dawned on me: while fast forwarding what would happen if you pressed the instant replay button instead of the play button? Answer: you automatically go back a few seconds just like TiVo.
So if this hasn't dawned on you yet, well, there you are.