As much as I would love toying with this, it really all about implementation.

There are a lot of issues to consider - what if I mean to swipe one thing but the system recognizes another? how is that handled? Does it calculate the position of my head and the perspective I'm seeing?

I agree with the above comment that this would ideally be an addition to our growing arsenal of HIDs, including keyboard, mouse, touch mouse, joystick, wacom tablets, and others are not intended to replace one or the other, most of them are complementary to other HIDs.

as a side note. Consider how many positions you can put your fingers into. Now both hands?

Now imagine if each position was mapped to a different shortcut...

How many unique positions could you map? (compare to keyboard).

I bet someone, somewhere is already planning an app where you downvote a post by flipping the finger.

Surely that would be a thumbs up/down motion in the manner that Romans used to decide the fate of gladiators.

Honestly a lot of gestures based controls of the floating in mid air kind are prone to tiring you out.

I suspect that unless there is some form of support, this may be like drinking Pepsi: Sweet on the first sip, but after a while, not as great.

Imagine surgeons who can't touch a surface with his/her hands due to hygiene concerns using it to manipulate various images/scans of the patient on the table in front of him/her.

You mean like http://www.zdnet.com/blog/health/xbox-kinect-helps-surgeons-... and http://www.bgr.com/2012/05/18/microsoft-kinect-surgery-surgi... ?

Well yes. If multiple solutions gain traction, it just proves that there is a market for this kind of thing. It's not about being first, it's about executing well. If Leap is more accurate for tracking movement, it could prove more suitable than the kinect.

Stenography machines have at least 22 keys. You can press any combination of them simultaneously, so over 4.19 million.

See: http://en.wikipedia.org/wiki/Stenotype

The problem is one of digital vs analogue, and ballistic vs servo. On a keyboard, you either press or do not press a key, and assuming that your finger is aimed somewhere in the right box, you need no visual feedback to see where it is and which thing you're touching. You also get the tactile feedback of "yes I hit the key", "I hit the key but it was at the edge, better recalibrate", etc.

So while there are a basically continuous range of positions you can put your fingers into (and with fifty or so degrees of freedom), the differences between many similar positions are subtle and require feedback for you to see which of them you're in---looping in your visual system and slowing down the interaction considerably. Which is what you want for certain sorts of continuous-ish interactions, and not at all what you want for certain sorts of digital-ish interactions.

All of which is to say, this sounds suuuuuper cool, but it's not going to replace the keyboard.

Agreed. It reminds of when the iPhone introduced people to the idea of an on-screen touch keyboard. Many people said they didn't like it and would keep using their Blackberries. How's that working out for RIM these days?

The point is that if the technology works (which is the important question, IMO), then users will adapt and embrace it.

The touch screen keyboard is still inferior to a hardware keyboard for typing. There are other reasons that companies produce more touch screen only devices and people buy them. Style, cost, simplicity, larger screen etc.

Language is a powerful way to interact with systems. With the mouse, we got first a single primitive - point and click. That vocabulary expanded to drag, but still that's about it. With touch interfaces, we got swipe and pinch thrown in. The kinect expanded that with body gestures. Following that trend, it looks like leap vastly expands our visual interaction vocabulary, or at least has the potential to do that. Considering all the things human hands have made in history, it would indeed be a shame if our computers thought of us as one fingered two dimensional entities!