After a couple hours of use, here's my initial take on the QMD product:
My QMD also arrived very quickly. I ordered it on Wednesday last week, I hadn't been checking the mail, thinking I'd see it on Monday or Tuesday. Right before Superbowl kick-off, my wife goes and checks the mail and brings in the QMD package.....good news it was surprisingly quick, bad news I didn't watch much of the game.
The packaging was very well done, everything was received in good order. I don't have an android based phone or tablet so I downloaded the free software to my Windows 8.1 laptop. After having to do a Java download and figuring out how to turn on my laptop's Bluetooth transceiver, I had the QMD up and running in about 15 minutes.
I started using QMD by setting my laptop on the long rail and shooting the cue ball strait from the head rail to the foot rail and having the cue ball come back and contact my cue tip. I quickly learned that didn't work very well, I'm guessing it's because the QMD records a shot when still motion is followed up by an impact to your cue tip. I'd often get two shots registering, the initial shot and then when the cue ball came back and impacted my awaiting cue tip. I simply altered my procedure and moved my cue tip out of the way after a reasonable follow through. This gave good results, shots were being recorded without the phantom shots.
After each shot, I'd look over at the laptop that would be automatically playing a loop of the last shot recorded. This gave me very useful immediate feedback, better feedback than other methods such as having an observer, shooting in front of a mirror or video taping myself. The graphical representation of my shot in the QMD software in conjunction with observing the cue ball direction and spin gave me more of an "under the hood" or micro analysis of my stroke.
The fun really started when I began experimenting with adjusting parameters of my stance, grip, bridge etc. to see how it would impact the straightness of my stroke. I'd shoot with my third and fourth fingers wrapped around the cue grip then shoot with them relaxed and away, only gripping with my thumb and first finger. The differences were readily apparent.
With QMDs help I made a minor adjustment to my back foot placement that yielded less stroke error. I think it's already helping me fine tune my mechanics which is really what I purchased it for. I would probably eventually find and make these same adjustments, I just think QMD aids in making those revelations quicker than one would without it.
Another variable that I was able to use QMD to see the difference in was using a glove on the bridge hand vs. not. With the glove, I was able to tighten up the pressure on my closed loop bridge and it would reduce some of the variance in my stroke errors. Without the glove, I couldn't use as tight of a bridge and I'd get more error in my cue tip placement.
I had my wife take a few shots and was able to quickly show her how her natural elbow drop was raising the cue tip just before impact with the cue ball. To the naked eye, it usually looked to me like her elbow drop happened after cue ball impact.
I've been working on slowing down my back stroke, the QMD velocity graph does a great job showing me how well I'm doing in that area. The velocity graph showed a very quick forward acceleration in my wife's stroke with a quicker transition from back stroke to forward stroke as compared to mine. She's now working on developing a smother transition.
Another item QMD identified was that if I use too forward of a grip in conjunction with not addressing close enough to the cue ball that I may impact the cue ball after the cue tip has hit its maximum velocity and is actually decelerating. I'll choke up with my grip hand to try to get higher cue tip speed on occasion, especially in break shots. In the future I'll be more aware that I don't run out of arm travel before tip contact with the cue ball. This was one issue I never knew I had.
Overall I'm very pleased with the QMD product. I definitely recommend it and I think it provides a good value, especially to someone who's time is at a premium. I have a time consuming career and am always looking for ways to maximize my improvement with the table time I have. Sure, a video camera and careful analysis/editing would likely show me the same things QMD did but that would be more time consuming. Bottom line, if you're curious about this product like I was you'll likely be happy with it.