All very interesting. I have lag issues all the time, but I admit I have been too lazy to really analyze them in an attempt to assign blame.
Tivo often seems to lose audio/video sync. Is it in the shows, from Tivo's own VP, from my receiver's VP or my TV's VP?
My DVD player is the worst. I blame it on a poor HDMI implementation. Don't buy DVD players from Yamaha - I have had nothing but problems with this POS.
XBox on the other hand seems great. I would guess it's because you don't normally watch people talking on XBox - and if someone is talking during a cut scene, I usually am just wanting to get past it to get back to shooting or blowing up stuff ( who needs story lines?
A lot of receivers can't video process HDMI yet, so I would guess lag issues are generated at the source, or at the TV. There's no reason I can think to blame an AVR for lag, when does not appear to have an HDMI video processing.
For those receivers which can, it's certainly possible some are adding lag.