Home-Grown TiVo Stories?
I am really surprised that no one has mentioned Windows XP Media Center. It has one thing that many other apps lack, the easy User Interface. http://www.microsoft.com/windowsxp/mediacenter/
Right now you still have to buy Media Center box from a vendor like HP, but the OS is already on the filesharing networks and someone release a hack to any XP Pro machine to turn it into a Media Center. (Its on sharereactor.com - an emule network)
I am putting together a high end entertainment system for my non-technical Dad and this seemed to make the most sense.
Also, Anandtech did a nice review: http://www.anandtech.com/showdoc.html?i=1766