Just curious what people think about the ENTER_FRAME event?

I've been using some scripting i found online to scroll a background, but it's very jumpy. The mouseMove event is used to trigger the scroling event which then repositions the Bg with event.updateAfterEvent code.

Problem is if you move the mouse too quick it doesnt move the Bg until you stop or slow down. Doesnt make the whole thing look very smooth.

I could probably get around this quite easily by changing it to an ENTER_FRAME event to update the background, but isnt the ENTER_FRAME event something to be avoided if possible? something to do with it clogging up memory and slowing the swf down if left running too long?