I've had this shoulder rest for about a year and found it very comfortable and useful. Easy to install too and stays on the instrument with the fairly gentle rubber grips, even when storing the viola on my "Travelite" stand.
The only gripe is that the adjustable length rods are a bit stiff even when you undo the screws which hold them in place. So it could probably do with some cork/slide grease or tiny amount of furniture polish to get the rods sliding more easily.
An additional plus side is that I can reduce the distance between the grips (the two ends of the rest) right down to fit a full size violin too. I would not use this for anything smaller than a full size violin though. So it is a truly versatile device, which is designed for all sizes of violas and for some people it may also be comfortable enough if you have a full size violin too and want to use this shoulder rest with both instruments.