I've recently been using a Windows DVR Application on my HTPC for controlling my DirecTV receiver and generally using my computer as a TiVo (without having to pay the monthly "Guide" fee). I've quite frankly fallen in love okay, I like it a lot (my wife wouldn't like the love thing much).
I still love my MC for Audio/Video library organization and playback, which is what I do mostly, but for capturing video with my Sapphire ATI Theater 550 Pro card, very little can beat a real DVR application. If you haven't ever used one, it basically works just like a TiVo and can control external cable boxes and satellite dishes using either a serial cable or an IRBlaster. I slapped a 320GB drive in my HTPC and I've got a TiVo like no other to feed my MC Library!
I've got to say though. The field of DVR applications currently on the market is quite disappointing. I often find myself wishing that it could be integrated better with MC, and way less stupid in most ways. This quickly leads to the thought/wish/hope that JRiver could do something better. That being said, these apps aren't simple beasts to design, and they usually cost quite a bit of money (mine was about $70 and I really needed to buy at least the Theater 550 card for another $80). Microsoft's MCE is even more expensive (and is a whole OS -- no thanks, talk about bundling)!
I would love to see what innovations JRiver (with their customization capabilities and organization mastery) could bring to the HTPC-DVR world. The question really is, would we be willing to pony up the cash if they could put out a quality product (as I'm confident they would)?
I obviously am. Any other takers?