IMHO I think that this feature is a 'must have' for all HT receivers. One of the most common complaints for HDTV users is the loss of sync due to the difference in processing times of video (up/down scaling) and audio (decoding). Nothing worse then watching LOTR and having flashbacks to my childhood watching badly dubbed 'Kung-fu' and 'Godzilla' movies.

I have heard that this is great to have but I feel left out. I watch HDTV all the time I have never had to use it......not once.

My guess is that there are a number of factors that can increase/decrease this problem.
a. video hooked up directly to TV vice through receiver
b. what resolution of the video was before it goes into TV and is upscaled/downscaled/de-interlaced etc
c. quality of video decoders

It is a good thing not to have this problem

I worried about this problem before I got my receiver but I have had no issues with my Sony direct-view CRT HDtv.

From what I have heard, it is typically seen in certain display types and certain brands of tvs, but it seems to be a less common issue.

Yeah - I notice the lip-sync problem on Samsung DLP displays a lot. The earlier models had a less sophisticated upscaler, I believe, than some newer models, resulting in a lag between the video and voices. It varies from channel to channel, and set to set with the Samsungs, even within the same model year. My neghbor had to take hers back it was so annoying. Nonetheless, when she got her Axioms, we made sure to get a receiver with an audio delay, just in case.