Good points. My motivation was Conan's new show on TBS, but then the other channels in the Expanded lineup looked like they could be worthwhile. Of course, I already have a lot of stuff to watch, so yeah, cable probably isn't worth it.
I still may want to build a box to back up my PC to, as well as stream media around the house. I still like the looks of the HP MediaSmart servers, as that would probably be the most painless solution for getting the features that I want. What could I gain (and lose) by building my own? Should I wait for a new version of Windows Home Server? I haven't done nearly enough reading.
