(Please scroll down for an update)
(VR Info added too)
I don't like giving negative product reviews, but I feel like this device may be a bit misleading for some.

Originally, I was very excited about this product. I tinker with things like the Microsoft Kinect, 3D mice, motion capture equipment and the Oculus Rift, and I thought this device would be a 'Kinect killer' of some sort. At one point during a press video, the Leap is shown displaying a pointcloud of the operator's hands, suggesting that the device was actually generating said pointcloud to do its calculations.

In reality, the Leap Motion actually uses complex algorithms to generate a best guess as to the position and orientation of the operator's hands. When you turn your hand sideways (not flat as shown in the pictures), it instantly loses track, so all gestures must be with a palm-flat orientation. Additionally, when you close your hand into a fist, it panics while trying to discern if it is seeing a fist or a single pointing finger. These things place huge limitations on how many, and what types of gestures one can make.

Please note that I tested my Leap on two computers, both with more than enough processing power, and both with USB 3.0. I ran all of the diagnostics, used the latest version of the software and drivers, and made sure environmental factors such as bright sunlight were not interfering.

Even with my precautions, I've yet to find a single app that allows me to do anything that can't be done with a mouse/keyboard or 3D mouse. As a pointer device, there is too much interpolation (Your finger will be stationary, the device will 'zero in' on its position, causing the on-screen pointer to slowly slide into place) and no 1 to 1 accuracy. As an audio controller or game controller, the device has a shockingly high failure rate at discerning gestures, making it unusable outside of a bit of playing around.

-This device will not provide skeletal tracking of your finger joints. I know it looks like it (see the main image with the blue background), but the joints shown are rough guesses as to where your fingers are.
- It cannot currently interpret rapid gestures like sign language, you need time between each gesture for the software to catch up, and you need to start each from a neutral pose it can understand.
-Because our displays are 2D, navigating 3D space is actually quite difficult, and is better left to 3D mice. It is fun for a minute to zoom around on Google earth, but it is still inferior to using another device.
+The Leap is a fun little device for impressing your friends or making a UI look high tech, but it isn't practical at all.

If you want to play around with the cool new technology shown here, or if some circumstance makes using traditional interface devices difficult/impossible, the Leap may be just what you need.

If you wish to use the device for anything practical outside of the above situation, or if you're expecting this device to be like a Kinect for your hands, wait for the next generation or for support of multiple devices. It simply isn't ready. It isn't fast enough, accurate enough, or mature enough to replace anything you already own. I applaud Leap and their break through, especially their reasonable pricing, but it just isn't there yet.

***Update 4/25/2014***
I have added one star to my rating of this product. After posting my review, I (and probably many others) was contacted and given a chance to take a peak at the updated software which was under development from the folks at Leap Motion. They were attempting to address some of the issues such as the one's noted in my review.

The results thus far have shown a marked improvement in latency reduction, joint tracking and accuracy. At this time, I still have no place for the Leap Motion in my array of hardware I use to interact with computers. I have high end joysticks, 3D mice, tablets, Microsoft Kinects, an Oculus rift and so on. Suffice to say I have many ways to interact with my machines. The Leap remains unplugged. My mouse still allows me to click icons and buttons faster and with more accuracy, my 3D mouse is still the only way to navigate 3D space and my wacom tablet is still the only device to be used for drawing or gestures.

I added a star primarily because the folks at Leap Motion actually seem to care about producing a great product. Unfortunately, at this time though, the product doesn't suit my needs, and my needs reflect those of the majority of computer users.

There is one area where the Leap may be truly useful though, and that is in the VR space. The current software release allow the leap to work while attached to the Oculus Rift. I will report back on this subject once I've tried it first hand.

***Update 4/26/2016*** All About VR
The developers behind the Leap have been working this whole time to improve their software. The latest drivers are the best yet at tracking, but VR is where things really shine.

You can get a bracket to attach your Leap to your Oculus Rift, DK1 or 2. I'm not sure how well it would work on a CV1 yet, but I'm sure they'll make an updated mount.

Once strapped to your face, the Leap can be used to track your hands within supported VR games and programs. There is an official demo for what they are calling Orion. In the demo you can create boxes by pinching your fingers together, and you can stack them, throw them, turn off gravity and toss them around. It sounds silly, but it is very compelling. The tracking was twice as good as it was when I first wrote this review.

As a consumer, if you find a program or game that uses the leap in VR, you probably won't regret buying one. But as a developer, there are still some issues. For me, the current implementation of the Leap in UE4 is just broken. My hands do not get attached to my character's body, which makes the whole thing useless. There is also the problem of the Leap's field of view. Since it can only track my hands when they're in front of me, I am limited in how I can use said tracking.

With that said, the Orion improvements are quite stunning. Should I find an app or game that is anything more than a few minutes of fun, I'll be adding a star or two to this review. Sadly, as of now, the device still doesn't do anything truly useful beyond novelty.

This review is as a UI developer interested in new ways to control both 2D and virtual environments.

Before you judge it's ability to track movements, make sure you actually check out the visualizer in the control panel. Don't judge on the basis of a lot of the apps, which don't always translate the hand movements as well as they could.

It does tend to get confused any time your hands are very close together or fingers are blocking other fingers, etc. This should not be especially surprising and is not something they'll likely be able to mitigate any further than they already have until they do the obvious and make it possible to add a 2nd sensor mounted on your screen to fill in the missing data that the software is currently doing best-guess work to fill in. That said, I think they're making excellent use of the limited perspective difference they have from those sensors in a product this young.

What I have here is a very cheap way to start implementing wave of the hand type stuff, pinches, 3D manipulation, etc. There are some gestures that simply aren't going to work as well as others and that's okay for now. It's still opening up a whole world of opportunity that I'm looking forward to experimenting with and I don't think there's enough people out there taking a step back and going a little more abstract with 2D interface stuff.

Getting it to run was as easy as it gets. I plugged it in. Drivers installed. I downloaded the core app from the web and immediately started using it.

Whether this is a great product for non-developers really comes down to the quality of the software taking advantage of it and whether you have any use for it. In that regard, it certainly isn't indispensable yet. But for what it actually is, which looks like 3 IR sensors split about an inch apart looking to isolate and make sense out of your hands and forearms, the core software is doing a great job. The rest is up to the apps and the huge UI conversation that's starting to happen around these technologies.

If you're curious about it and the cost doesn't require severe adjustments to your weekend plans, you'll definitely get a few hours of fun out of it and have something neato to show friends/family. That's not really a waste in my book but I suspect this product or something like it will eventually be standard equipment on laptops and possibly keyboards/monitors for desktops. With a second perspective angle, it should work brilliantly, but even with just one, it opens up worlds of possibilities.

I thought I could be more patient than those providing negative reviews. Unfortunately, this device is simply very inaccurate. The primary issue is the camera reads context through a 2D identification method. No depth perception causes a large number of misreads and jumpy behavior.

Leap is working on the ability to combine two Leap Motion sensors to provide increased accuracy, however that simply shows that a single product is weak in itself.