The only advantage of the CM7 is the second softer massager motor that I never use and so I find that the CM5 was the best value of the bunch
I have now tried the CM3, CM5 and CM7 and my final opinion is that they likely all have identical percusion mechanisms and so the price differential really shouldn't be so extreme.  The CM3 is half the price of the CM5 but feels slightly cheap by comparison and makes a bit more noise as a result.  It also lacks the speed control.  The only advantage of the CM7 is the second softer massager motor that I never use and so I find that the CM5 was the best value of the bunch.  It has a more solid body (same as CM7) and dimming function but comes with less of the useless extras.
Rating: 3 stars