Cornerman wrote a great review and I'll refer to it throughout my review/comments.
I purchased my Digicue(r) retail so my review is completely objective. It is also subjective in that my evaluation is based entirely on my opinion and not on any scientific testing.
Overall: I like the product and it has definite uses. Possibly more useful to the less experienced player than to a high level player. Tactile feedback after every shot goes a long way in reprogramming a brain.
Fit: Like Cornerman, I found the fit tight on some cues. On my shooting cue the sleeve had to be stretched a little. When it was time to remove it the vacuum created made it difficult to remove without damage. I solved the problem by adding a small hole for air to enter breaking the vacuum. How? It's not a good idea to just poke a hole in the rubber sleeve since that would make it prone to easy tearing. I used a small (1/8") brass tube, sharpened the end with sandpaper, and used it as a mini hole saw to cut out the relief hole. Worked fine, just put the sleeve over something (not your cue) to back the rubber while cutting it and take your time. I did the job by hand, not wanting to chance cutting something I couldn't replace easily using a power tool.
Inserting the device in the sleeve: After a bit of head scratching I grabbed a short length of scrap 3/4" dowel, attached some double-sided tape to one end, and used that to install the module. Worked great. When it was time to replace the battery I used the same idea to grab the module and remove it. Took a bit of rocking back and forth to get it out of the sleeve but it worked fine.
Sensitivity: Also, like Cornerman, I found it difficult to not get "buzzed" on draw shots. I have multiple shafts for my cue and decided to see if I could tell a difference just by changing shafts. Yep. Hit 50 balls with each shaft and tried to keep a constant stroke throughout the test.
Shaft 1: Maple shaft that came with the cue (Adams version of Helmstetter). Solid maple, normal taper, 13mm Kamui Super Soft tip. It was not difficult to hit draw shots and avoid the dreaded buzz with this shaft.
Shaft 2: Dominiak D3, laminated, normal taper, 12.75MM tip, Kamui Super Soft tip. Took a little more work to avoid the feedback buzz.
Shaft 3: Bob Danielson, SS2 with a special taper (no taper for the first 14 inches), 12.5 mm Kamui Super Soft tip. This one, probably due to more vibration, took more effort to keep the Digicue happy
Short version of my perception. The more flexible the shaft the more prone to getting feedback buzz. Hitting the table with the cue tip tends to make it likely you'll get buzzed. I tried to hit some draw shots without hitting the table with the cue tip. It does seem the Digicue complains less often. However, this isn't a "correction" I'd make in real life.
I took the Digicue to my favorite billiard supplier, Southern Billiards in Loganville, GA, and asked several folks to give it a try. All, like me, thought they had a smooth stroke and were surprised at how often Digicue said "not on the that shot, you didn't." And, like me, after 10 minutes or so of using the product were getting buzzed less often. Based on that alone, the thing works.
Final thoughts: It works. It may not be the cure for all stroke maladies but the instant feedback promotes rapid improvement. I think the less experienced a player is, the more quickly it will promote improvement in basic stroke skills. After all, no matter how much you know about how to make the shot, it ain't gonna go if you can't hit the target and avoid unwanted spin on the cue ball.
Cheers y'all,
Southern Fried
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