The trouble with Tivo is when there is a problem you may as well be on a deserted island.

Cable Co - It's not our fault
Tivo - It's the cable card's fault
Customer - It's your fault, you told us to get it
Distributor - There's nothing wrong with the hardware, your problem

Been there, done that. It sucks.

Yes Mr. Customer Tivo is wonderful, however your local cable company's firmware and the new hardware aren't compatible and there's nothing I can do about it.

If it works on your system, lucky you.
If you're on the big C, it's just a matter of time until you get the ONE that just won't pair right, no matter how many cards, calls, tech's you throw at it.