I think that communication with reader is problem here. When re-runing video, it's already in the computer's cache, hence no delay.
But if sound is synchronized with video when playing from computer's hard disk, I wouldn't bother
Some digicams had really unsynchronized sound. In case of my Pentax 750, delay was about 330 ms, so I had to correct audio gap before converting to mpeg/divx format. On my A620, there's no such problem