Looks like Neversoft patched Guitar Hero III recently to match up with Rock Bands ability to move both the audio offset and the video offset. However they took it once step further and made the auto calibration process two step (step 1: Sync with the clicking noise, step 2: Sync the video circle with the circle on screen). This is probably the best test of what kind of offset you should have on your TV for these types of games to date.
I have a Panasonic 42" 1080P plasma running the video from my Xbox 360 through a Denon Reciever, and found that my video lag was around 30ms and my audio lag was around 10ms.
The results for this lag calibration tool were absolutely fantastic. I know if your anything like me, and super anal about the calibration, this is great news. I was about to apply the 10ms offset to rock band with a 30ms video offset and have had great results. Hammer ons on Green Grass and High Tides feel tighter than they have felt to date. Was able to boost my high score up on this song by 30k to 350k+ which I'm pretty pumped about.
Anyway grab the new patch for GH III and check out the new calibration tool .
Wow. This sounds great. I always had trouble with lag with IIDX with my HDTV. I am glad they work to fix this and it has real effects that are positive.
Note to HDTV ownerse playing GHIII or RB... 
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