Thanks I have 2 and love them. A change to my configuration and lifestyle has prompted me to prefer to have the ability to use either my amp OR tv speakers, depending on who is watching or what is being watched. HDMI CEC allows me to avoid having to duplicate every activity (one put together with the amp on, using amp for volume, and one with amp off, using tv for volume) because if I turn the amp on, it will forward volume commands sent to the tv to the amp. So I just have one activity that can handle both cases, HDMI CEC will decide where the volume commands go, which I really like, didn't like using extra activities for almost the same task.
Anyway, I found that I could connect another optical cable from the tivo to the TV input on the amp, and moved the optical cable that was going to the tv input to another one. This way, whether the amp is on CATV (HDMI) or TV (optical), I'll get the sound I want. I had been avoiding this move before because I had an htpc hooked there (CATV) before and didn't want to use optical at all, but now that's on another input and I don't think the tivo can put out a signal that is too fat for the optical to handle, like the HTPC can.
Ironically, now that I've done all this, after testing it a few times, the TV input is not getting annoyingly switched to anymore. Still scratching my head on that one but whatever, it's working now, I'm not touching it!