I don't bother on my own car - if you have a decent LSP product on your car, any decent pressure washer will do the same thing, unless your car is exceptionally covered in crap.
For Customers' cars I tend to use it, but normally to get good coverage of shampoo so that I can work it in on plastics etc, before hand washing. It looks good too.
Any effective ones are normally too potent for their own good; they will degrade your wax/sealant quicker than if you don't snow foam. Anything mild enough, won't shift more than your pressure washer anyway...