I think the newest version of the Fusion card can decode cable HDTV, in USA anyway, the QAM standard or whatever it's called. It seems I had heard another was going to support cable HDTV but I can't remember, may or may not have been a newer pcHDTV model. avsforum will know for sure.
The bick sticking point for USA users is the future of encrypted cable HDTV. Rumor has it that Comcast does not encrypt the "local networks" stations, but you'll be out of luck if you subscribe to HBO HDTV or other premium HDTV channels, as well as much of the digital NTSC channels which are encrypted. I'm suprised no one as made a tuner card that accepts the smart cards so it can legally work with all channels you've subscribed to, encrypted or not, or at least made a PCI smartcard reader that can be used on the data coming out of the "dumb" tuner card.