I've owned one of these at my previous house. At first I was not sure about the additional cost of this product vs a normal or even premium electric shower, but that soon disappeared once I had a shower!
Its a very powerful shower and I'd recommend it highly, in either exposed (pipe from the ceiling to avoid damaging existing decor) or on the wall mode (hidden pipework, best if renovating a bathroom).
Retail prices are £600+ but on ebay you can get them for £350 to £400 depending on your luck (and only buy from those with substantial feedback) brand new with 5 year guarantee. At this price they are superb value and I've bought again at my new place.