MythTV is working. This morning's repeat of last night's "Daily Show" plays back on my living room TV via the TV-out port of the Hauppauge PVR-350 card. The information overlay does not slow down the hardware MPEG-2 playback at all.
This is the hard part. I'm recompiling now to add native LIRC support. I need to get X running so I can run mythTV's front-end on the TV itself. At the moment, it's running via remote X on the iBook. I need to get the cron stuff running too, and then configure the UPS daemon.
So far, the commercial detection seems to work properly too.