byopvrs are not worth it when you can get an actual Tivo for like $50.  
Depends.  Unless you hack your tivo you can't get the video files off it and burn to dvd.
If you just want to record TV, it's hard to beat a Tivo.  But a BYOPVR takes TIVO to the next step, turning yout tv into a media and information center.
Ok, you can extract some shows to pc.  But soon probably not many.
http://slashdot.org/articles/05/09/14/1440252.shtml?tid=129With something like GBPVR, there's modules to read RSS feads, a weather module, shoutcast module, jukebox, movie theater listings, etc.  I think MythTV has a feature to connect with Caller ID and show the info on screen.
The cost.
If you already have a PC (say the one in your arcade cabinet that isn't doing anything when you aren't playing it) it will cost less than $100 to create a pvr system with tons of features.  For another $100 you don't even have to have the computer in the same room as the tv thanks to MediaMVP.  To start from scratch would cost less than $300, you only need a <$100 WinTV PVR150, <$100 1-1.5ghz computer, $50 150gig hd.  That's new prices, get a used pvr card from ebay from someone who upgraded to a pvr500, and a used 1ghz computer...
And then since it is a PC hook up some usb gamepads and play nhl2k6 with your friends 

 or even mame  

But then again I believe a tivo can do most of that aftering being hacked...
The funny thing is since I have a networked computer in my arcade cabinet it has become the information center.   Like if we want to find an address, phone number, theater listing, order a pizza, etc we fire up a browser on there instead of my main machine since te arcade is there in the living room 
