Navigation/Rotation is inherited from the original Java based World Wind in an effort to provided similarity to users wishing to change platforms. A little different from the arcball-style, I agree, but at least there is a reason :)

There are plans to add momentum gestures to our Android platform (https://github.com/NASAWorldWind/WorldWindAndroid). Perhaps it should be added to the Web version as well?

I like the momentum, but on mobile (iPad) each move is a new place in my back history.