I bought one as an experiment a couple of years ago.
It wasn't bad. Slow, but it worked. It came in handy for inflating a paddling pool, and for topping up car tyres, as well as a few bikes.
But it's now gathering dust as it hasn't really inflated the last couple of times I've tried it. Not sure why, maybe a connection isn't air tight or something.
I toyed with the idea of upgrading to a Fumpa, but never got round to it.