Thanks for that info. I am a PC Tech & am inquiring for a client that I will be doing a job for later today. I don't have any Comcast/DVR firsthand experience so I needed to do some quick research.
I did a quick search & discovered this on Comcasts FAQ page;
"If you choose to use a CableCARD device instead of using a Comcast digital converter or digital adapter, you will only be able to receive one way digital cable channels and will not be able to receive OnDemand, pay-per-view and the interactive programming guide. "
That's kind of a bummer. So if you want to take advantage of PPV, program guide, etc., you are basically forced to buy/lease Comcast's equipment.
a tivo has its own guide, but you will not get on demand unless you rent a comcast box. on demand is just starting to roll out to tivo's in select markets but its going to be a while before its a nationwide program. right now its in areas or san fran.