I have a Mythbox that I built well over a year ago that I absolutely love. And as long as it's working correctly, my wife loves it to. One of the really cool things about it is that I have all of my DVDs available on demand, along with all the recorded TV shows (think AppleTV and Tivo having a Linux-baby).
Having movies immediately playable from a menu is teh awesomes. However, this requires an enormous amount of storage space. I don't have enough space in the nice Mythbox case that's designed to look like an entertainment console rather than a beige box computer. So I turned my existing Linux server (which handles NAT and firewalling for my home network) into a storage server.
For almost a year, I had three 500GB drives merged together via LVM to make a 1.4TB volume to contain all my movies. This has been plenty of room, and thanks to LVM, all I need to do later is add more hard drives and extend the volume.
However, this has no failure tolerance. One drive dies, and the entire collection is lost. Yikes.