I've just got my Move Gun Attachment (actually, two of them), which I've anxiously waited. The product itself is solid, nice and fits perfectly in hand - a true Sony quality product (but hey, I went for the best, didn't I?). The Move Controller is easy to attach/detach and fits perfectly. The resulting gun is well balanced, not too heavy and not too light, feels just like a real gun. The upper part is transparrent, so you can see the controller's red light through it, and all controller's buttons are easily accessible. You can even keep the wrist strap attached to the controller, and you may charge the controller via USB cable while mounted in the gun. The trigger can be pulled with ease, and using the gun requires a minimum effort (less than using just the Move Controller alone).
However, in terms of playability the gain was less than I anticipated. The only game I had to test the gun was the demo for The Shoot, which I've got in the Move Starter Pack disc. I expected to be able to actually use the gun as a real gun - including aiming. But that was not the case, since trying to do that resulted in erratic moves of the aiming cursor on the screen. The result was really disastrous when I had my arm fully extended and tried to aim by moving the whole arm rotating from the shoulder, as in real life. I achieved a correct response only when I aimed the gun by rotating my hand from the wrist, similar to the moves the controller makes when kept directly in hand (as if a shot cowboy-style, from the hips level). Doing that with my arm extended for a longer time would be uncomfortable, so I had to keep the arm semi-folded. I guess the aiming-related inconvenient is a matter of calibration and might be limited to he Shoot (or maybe just to the demo of it), but again, that's the only game I tried the Gun with.
As an overall conclusion: the product is of really good quality and makes a nice addition to the PS3 Move Controller, but using it brings less fun than one would anticipate. Hence, I'm not still convinced it's worth the money.