I've now used this five times in two days. Washed two cars, cleaned the lawnmower and whipper-snipper, lastly the outdoor wooden table and benches. It's is excellent.
I highly recommend it. It's so good, I might buy a second exclusively for my car foam.
Some people say "it leaks". This is BS. It comes with a little roll of pfte tape. The loops on each end of the extension piece, wind it on positively and presto.
I've used this with a 20% solution of industrial degreaser and it foams mightily. If it's down you want to generate, then perfecto!
Negatives? None. But I would say that I'd prefer the foam action knob on the front to be a bit stiffer, second, one must be careful to wind the bottle onto the brass thread correctly. There is a possibility of a cross thread. It's a chunky thread and the brass female is equally so, but I've found in use this could cause strife amongst the impatient (and incompetent). Keep this trivial thing in mind and you'll be fine.
Positives? Many. Í was incredibly surprised at the very solid build of this. It is very well made, with generous brass, finely fitting (and well cast) knobs plus a good thick bottle. It is obvious this could be used heavily and not experience troubles.
I'd give this a 10/10 and completely recommend it.