Currently i'm using the opensource mediaportal on my main pc, with encrypted digital cable.
The reason for not using mythtv is that i play games on this machine too, that don't work too wel with linux.

It can do pretty much the same as mythtv (i think, haven't used mythtv) but is a bit simpler to set up.

Mediaportal has a cool new trick in the beta version: recording and/or watching multiple streams with 1 encoder, as long as they're on the same transponder