Yeah they are really good. The way the brush swivels around just feels natural and you start doing it automatically, after using one you'll wonder how you got by without one. Gaz'z brush is really good better than a vikan in my opinion, but I don't think it's the best around I'd like to try a swivel on some different brushes.
You do need a stiff pole to use the swivel effectively though, that's a short GF not a long GF if you are going bigger something stiffer.
Simon.