I have a MythTV backend with 4 tuners. 2 Asus Falcon2's (PVR-150 like), and an HVR1600. The HVR1600 is a dual tuner with analog and ATSC/Clear-QAM inputs.
This setup has been running for roughly 3 years, with the same issues.
/dev/video# ordering -
Upon the rare reboot, the tuners would reorder themselves. Considering the Falcon 2's use IVTV, and the HVR1600's analog tuner uses cx18, this can cause issues with MythTV. Usually I just resolved this by quickly running mythtv-setup...