Sorry for the late reply. My basement just got trashed after a winter thaw and just finished having it waterproofed. My lab was down there, so I haven't been playing with LinuxMCE until now.
In answer to your question, I'm just using the Hauppage PVR150 that I used to use with basic Adelphia Cable. I know it works with Fios through the composite in jacks, but its not HD. Currently, I don't care, because we only have one HDTV.
I wouldn't use IR to control the box, you can use a serial cable and modify the changechannel.py script that comes with the MythTV bundle. I'm going to look into how to submit the revision to LinuxMCE, but currently, I just want to get it working.
Question for you. How are you handling the Remote Control issue? I really don't want an ugly IR dongle on my media directors. Having 7 media directors, I'll bet you found a cheap elegant director solution.