I have 3 DVB-s cards in one machine, 1 is a FF, the other 2 are budget. I run in softmode using softdevice 100% of the time. Even though I don't receive and HDTV at all, using the output of a VGA card into a LCD projector produces a much better picture.
Displaying HDTV will need a powerful computer.
I might hold off buying anything - the upcoming Hauppauge HVR-4000 looks like the one I'll want! HDTV in my home area is likely to follow the DVB-S2 route