In my humble opinion it would probably make more sense if you see how many people 1.)tried and 2.)downloaded the Device.
At first I came here because I also wanted to have a review system same like amazon, but during reading I realized in the end that some comments are true, and that there is probably it is a better way to know if the device is "good" or "bad", useful or not.
For sure, if I want to know the sound of the device, I can listen to the demos on the page, go to youtube and listen, or download and try it myself. If I then realize I don't want it, I just leave it.
So for the ranking itself, there are some reasons why this also might not help, first if the price is too high, people who actually might want to have it will not buy it.
Second they realize they don't need the device and refuse to spend money on it. But, i the device it really good then people are going to spend this money, and you can see it has been purchased many times.
This information (both counter for try and purchased) would actually make more sense to me than a review system.