I upgraded my Gentoo box running MythTV to a new kernel and a new ivtv version. The only problem I had was that watching live TV no longer worked, and I need that to satisfy the wife even though we rarely watch TV regularly any longer. It seems the ivtv driver change the numbering scheme for tuners to start with 0 to starting with 1. Running mythtv-setup and changing the selected tuner from Tuner0 to Tuner1 made everything work again.