I've seen it used on several projects, and it is overkill, the only exeptions were sites I wouldn't have built in flash to begin with.

I've used a pattern that kinda mixed the model/view but it ended up being more of a mediator pattern in the end. In fact that's exactly what it ended up being - All child objects of the main singleton object corresponded to visual components on screen. It worked pretty well and suited flash development quite nicely, but that was AS2.