interesting. This is a huge thing for me too.
But to address some of the other comments as I use my mighty.
I don't really hold the mouse as I use the scroll. My hand kind of rests over the mouse with my pinky and thumb on the sides (not squeezing, just holding my hand in a hovering position.) I can swipe this mouse fine without touching it at all and it stays still. If the magic is heavier, it'll probably stay in position even better unless the surface is more sticky or the bottom more slippery. I tried the same with my phone and it slid. I can see that if that's the case, the magic will make my wrist sore. (but my wrist is pretty strong on the right side 😉 )
Actually, the app to make your phone a touch mouse is awesome... Who needs a trackpad when you've got a touch or phone.
I can't imagine that more gestures wouldn't be added. On that day, I'll buy it... Plus, the mighty still works mighty fine.