I know. Trying to look at the demo page while using a mouse with a scroll wheel was infuriating. (Stop! Wait! No, come back! No, not that far! Wait! Stop! WTFFF)

I had actually used d3's internal transition / tween functions to do something similar. Take a look: http://jsfiddle.net/x4EBe/

It's nothing fancy, but was quite interesting to have in a dashboard we made.