As I have blogged before, I'm a big TiVo fan. Had my Series 1 box for over five years. I've bought and sold their stock and made some money. On a regular basis I'm evangelized their product, but what I've heard more recently is - "oh I've got a DVR from my cable company."
They aren't the same, Sam's posting is a great example. The only problem for TiVo is that most people haven't experienced it. Their bar hasn't been set for a DVR solution.
I can't comment on how good the other cable company's solutions are, but my guess is they all use similar suppliers of technology. Similar sub-par performance.
TiVo needs to figure out how to reach all these cable DVR subs and show them their solution is better.