Well I still haven't gotten my insurance situation settled yet so I'm still waiting on that, but I did get a chance to put some rounds through an M4 today. I have to say that's one slick and refined piece of machinery!
The sights, the controls, the telestock, everything worked great for me, I liked the fact that the action took the edge off the recoil but didn't feel "uncoupled", spongey and distracting like some gas autoloader designs can when they cycle.
The only thing i didn't like, which I didn't notice when handling one previously, is that it seems surprisingly muzzle heavy for what it is, even when running empty. I don't know if I could get used to that.