I've tried a few different devices of this sort and the problem with all of them, and gesture enabled track pads to a degree, is predictability. If I use a mouse or a trackpoint, the behavior I get is predictable and consistent. These devices are a crap shoot. Even if they correctly interpret the gesture 99 times out of 100, you have to be vigilant against that one error. That interferes with the normal speed and efficiency boost you get from muscle memory and disrupts your thought process.
My other beef with them is the lack of tactile feedback. If I click a button, I feel the click. That does not exist with all this hand waving.