Well, when I was a student we didn't have a washing machine so my student shared house (three people), used the Wonda wash for about three years (exact same device as pictured, I am from new zelaand so it probably had a different marketing name). The infomercial that convinced me to phone up and get it (yes, yes, .. I know... the innocence of youth) said in just ten turns, a quick rinse and you're done, and your clothes come out better than a washing machine (it had fancy diagrams showing how the spinning motion was physically this and that, and that it was the mechanical motion of it that did wonders).
Well, it was more like 200 turns, two rinses, and I was done. But I have to say it never matched a normal washing machine. So it depends what you are after. If you are living in a rural community and just want relatively clean clothes, and have the time to bother with it, then it is fine (being a male university student from a rural sheep farming valley, time and worrying about clean laundry factored very low on my priority list... unless I thought it would be noticed by a female student).
So, it depends on your lifestyle. If you need white white shirts for work, it is probably not a good idea. And as far as just soaking with detergent in water goes, when I lived in Nepal, water was at a premium in summer, so for laundry I would leave clothes to soak with detergent in the hot summer heat for a day before hand washing. But they still never came out as clean as a machine. The locals (as is common in India as well) would just wash their clothes by beating them over and over again (basically scrunching up the clothes, one piece at a time, with water and a little detergent, and kneeding it like bread dough, and then after that they would swat them like they were a wet towel against the same boulder or rock). They would do that for ages, so I just paid local woman to do that for my clothes and THAT did wash my clothes every bit as good as a washing machine.
But it was bleeding murder on my clothes I can tell you. Any plastic buttons usually came back split. The detergent unfortunately was a huge problem there as the best place to do laundry was in a lake and the detergent from hundreds of women washing all day long caused algae blooms in the lake.