I had one. The concept is great, but I found the salmon brush very heavy and I just don't get on with fan jets.
I eventually put the switch gizmo on a lighter brush with pencil jets, which made a big difference,.. but it still adds 150 grams to the brush head. Fine for domestic work, but i found it hard going on higher stuff.
Now I just use a high visibility silicone pole hose from sureclean systems which is light & tough, and can be squeezed between my fingers to stop water flow,.. much easier & lighter IMO.