Many moons ago I dabbled with MythTV to record over the air TV. It's an open source home entertainment application. Then DTV came along and the tuner card hardware I had was going to need replacement.
Since then I have played with Kodi/XBMC, and OpenELEC on the Raspberry Pi. But I am using this much like a Roku box, just to compliment my TV watching. I often wish there was a modern DVR for over the air TV.
Recently when I was shopping the RCA DTA880 caught my eye. A digital converter box with recording. There is also the Ematic AT103B. Both can record over the air TV to a USB stick. This is awesome. Neither however have a network jack, as it would be nice to be able to play back/record to a network share. Another thing I wish it had was line input jacks, so you can record from an external source like a satellite.
Basically someone needs to combine these converter boxes with a Roku boxes for folks who are looking for options when considering dropping cable etc.