I'm Pete. As of May 2011, I've been trying to set up a Mythbuntu system with a Hauppauge PVR-150 to work with Comcast digital cable. I got pretty far, with the generous help of some folks on the #mythtv-users IRC channel; but was stymied first by the need to set up LIRC to control the TV tuner in the cable box, and then by a setup that stopped working and started giving me Error 139 (segmentation faults) when launching the front end.
At this point I'm thinking that MythTV might just be beyond me! I'm thinking about wiping the drive and starting over, getting a digital card and just working with broadcast TV instead of Comcast, which I believe would eliminate the need to set up LIRC.