I get 113 channels OTA here in Houston. With that many channels it's not uncommon to have 4 shows being recorded at the same time (especially older series that are broadcast just before/after midnight). I've been recording older shows like That '70s Show and watching them in order. Have seen a number of episodes I missed back in the day. Also recording cable series I'd missed in the past, like Burn Notice and Psych, that are now being broadcast OTA.
I purchase other cable series, like Dexter and The Walking Dead, à la cart from iTunes or on physical media. I've saved $1300 since dropping DirecTV in January (savings = old DirecTV bill - à la cart series).
I went a little overboard on the Mac mini setup (Drobo raid system, extra RAM, CPU upgrade, etc) so it'll probably be another year before the savings pay off the hardware investment.
If anybody's interested, I've been documenting my DVR Project in my blog.