Tivo and ReplayTV are hard disk based video recorders (replacement for VCR) but oh, so much more! You can "pause" live tv with the push of a button (it just keeps recording at that point, and you can begin play at a later time, even if the show hasn't yet finished). Random access, automatically programmable from a menu (you can record everything that has "light" in the title, for example). The latest ReplayTV is internet connected as well, and you can even transmit entire recorded shows to other ReplayTV owners. The have very good commercial skip now too.
I seriously want one, but haven't convinced myself to part with the cash yet since I don't watch TV much anyway...