I've always felt that if I'm sore moving helps get rid of the stiffness.

Maybe just gets the circulation going so lactic acid can be worked out?

I find this up to a point and sometimes I know it's not going to work because I'm too sore to even warm up properly - but thats pretty rare.

I wouldn't do heavy weights or anything but something more aerobic seems to be the go.

I always feel like I need more sleep when I'm sore too. Took half a day off yesterday just to sleep

I guess it's one of those things that everyone has to judge for themselves as individuals?