Yeah, def. the htpc would sidestep monthly fees. Although, it is just one layer too deep for guests and parents to turn on the htpc, wait for it to boot up, and then watch TV or DVR programs (at least with my 8-10 year old htpc all-in-wonder ATI radeon knowledge). I'll keep it on the back of my mind as something to consider, seeing as there are ways to make it boot up faster (standby/solid state drives) and there are low-power chips available so that it isn't a terrible drain on the electricity bill if it were to be on all the time. I'll have to check with verizon to see if they can offer a free fios/cable card or whatever it might be called. Is this a PCI type card or is it just an external box usually?
You wouldn't turn it off. The DVR records programs as it sits during the day and while you watch other things.
Every cable provider using cablecard is required to provide at least one cablecard in installation areas where it is required to receive service. Uverse (and other video over IP) solutions often do NOT use cablecard. They aren't subject to the same laws. I'm not sure how Verizon works, but I understood FIOS was fiber right? (Maybe not fiber to the home) TiVO and every other cablecard device only work with coax.
A cablecard is the size of a credit card and is inserted into a TV, DVR, cable box, etc. It contains an ID and encryption stuff that permits whatever device its plugged into - to decrypt the stream coming over the cable.
Recently Robert Heron builtup a 4 tuner box using the first widely available cablecard tuner . (in that case its a pcie card with a cablecard slot, and 4 coax inputs).
One thing to note - you do not get "on-demand" or the inbuilt program guide or any pay per view events with anything but a cable company box.
Also if the software running on the HTPC is DLNA, you can fairly easily get an xbox or PS3 to act as the front-end. So you have the HTPC running in a back room, and view programs on the game console.