Probably the most thoughtful and humble opinion we received from a professional was a declaration that -

"I had no idea my stroke had gotten so bad!  I think you have a great training tool".

A college golf coach suggested -

"My guys really like it...and not only helps the path of the putter, but also the rhythm and timing.  Overall I think you have a great teaching tool."

A Chicago low handicap amateur responded -

"I like that it requires you to make a very precise move in order to strike the ball correctly.  I also like the  instant feedback when I miss-hit the ball.  It tells me immediately what I did wrong, and if you continue hitting the ball incorrectly it tells you in no uncertain terms that you REALLY need to continue working on your putting.  But perhaps the best feature is that I find it really easy to transition to my regular putters.  The improvements stay with me and have increased my putting confidence.  It can be frustrating at times, but I guess that's THE POINT, right?"