I've wanted to build my own PVR for a while.
MythTV looks great, but I don't have the patience or recent Unix experience to work with Linux. Several friends of mine tried it but ended up getting stuck waiting for a driver for their video card. One of them broke down and bought a Tivo.
Plus, if I wanted to extend it functionailty, I would have to code in Java, a language I've left behind. I'd rather use my C# skills to develop modules on my own.
While the Windows world has Windows Media Center, Media Center PCs tend to be pricey. I'd much rather build my own box out of spare parts and components I can buy for less. Plus, I can run the software on my laptop, which already has video output and an ample 80gb hard drive. True, I wouldn't be able to record, but if I had a home pc unit doing the recording, I can set up my own personal streaming software a la Tivo to Go to watch from anywhere.
GB PVR runs on Windows, as does Media Portal. Meedio is also Windows based, but it's not open source. It costs about US$50, which isnt' bad if you already have the hardware. Meedio also has another product that lets you control devices in your house from your PC, for US$149.
[found via Extreme RAD]