I finally talked my wife into getting a Tivo unit and now she uses it way more than I do (she loves it and never wants to go back).
I don't feel like paying the $13/month on top of my cable bill, so we went with a Tivo/DVD player unit that came with the free Tivo Basic service (doesn't have all the bells and whistles of the "plus" service, but it allows us to pause live tv, record all of our shows and have the tivo program guide).
I think the byopvrs are cool if you have all those computer components laying around, but if you don't, it would be hard to get all of that stuff for less than one of these Tivo/DVD players with tivo basic service free (the one we have is Toshiba SD-H400, I just did a quick search and found it selling at
http://www.igotwired.com/tosdtidvddim.html for $180, I never bought from them, but the price seems nice).
If you really want the plus service after a while, you can start paying the monthly fee, and it even comes with something like a month of free plus service as a trial, but I never activated that because I know if I do, I'll be compelled to pay for their service in the future.
Tivo (or any PVR) is just like the scroll wheel on a mouse, when they were brand new before you used one you didn't seem to understand how convenient they would be, but after using one, you never want to go back to a mouse without a scroll wheel.