I picked up a Leap Motion controller the other day as a potential MIDI controller. Having downloaded the Geco MIDI app, I have been successfully able to link some gestures to MIDI events. However my initial experiences indicate that the technology and software are probably not yet at the level of maturity required for this to be a practical controller for most users.
Having said this the potential is quite extraordinary, if the software issues can be resolved. The controller itself can track hand position, pitch, yaw and fingers splayed and closed with extremely low latency - a few milliseconds - and it could become a truly incredible MIDI controller in time.
The current problems primarily stem with the Geco software rather than the Leap Motion controller and its associated software. I am currently in discussions with the developers to see whether the issues I had - primarily to do with reliable gesture recognition - are in the process of being resolved. To be fair, the app only costs 10 bucks, but it is critical to getting the Leap Motion controller to output MIDI, so unless you wanna write your own software, it's the most attractive path.
I'll post back when I have some progress on the issues I am experiencing. I'm really excited about the possibility of this controller given its low latency, and its ability (with some limitations) to track each fingertip position as well as your palm position, pitch and yaw, in real time. Certainly would make an amazing Theremin!.