Ohh i get ya. Never got to the stage where i encorporated it regularly into my game, although i have done it in the past. As you say though Rev, its probably a sign of a good player as when they go prone they have to adjust their aim to get the kill. Takes a fair bit of skill to do it effectively.
Oh and on that subject, has anybody noticed on the black ops trailers how you can do a running dive onto the floor to go straight into prone?? Looks ace!