What does the weight in the cam itself actually do? I see the bows w/ them are generally a little faster. But less than 10' or so. What's the big deal? Is it worth the extra $$$?

I belive that it is all for speed. It just makes the cam "kick over" faster. At least that is what I think. Maybe someone who actually knows what theri talking about can answer it for ya.

The original perimeter weights in the Max Cam did a few things. First and probably most important, it counteracted the forward motion of the limbs to reduce recoil or "kick" of the bow at the shot. It also smoothed out the application of force to the arrow by its mass releasing the stored mass over the length of the power stroke. The Max Cam and many other single cams did not store as much energy early in the draw cycle, but pulled harder at the end of the draw. The perimeter weight's mass slowed down the cam slightly during the part of the power stroke that matched the hardest part of the draw, and its momentum added more force to the last part of the power stroke, matching the early (easier) part of the draw. It may have added a few fps, but that was not the main reason for the weight. A smoother shot with less recoil was the main advantage. With today's parallel limbs, the weight does not seem to be as important.