I used the wonder wash and spin dryer for about a year before we had Ladybug and then I used it for a several months for her diapers. We did this because we didn't have a washing machine, but I would never spend money on the ww/spin dryer combo if we had had one. To be honest, for me the savings in water/detergent alone was not enough to keep using it and I actually found the rapid washer (the plunger type) much easier and quicker to use than the wonder wash. I did enjoy washing by hand, but it was too much work to do daily with a little baby around. We finally purchased a haier that hooks up to our bathroom sink (which cost only thirty dollars more than the ww/dryer combo when shipping was added up), we hang dry in our utilities room and I couldn't be happier.
However, I do love the spin dryer for spinning the last bit of moisture out of diapers and sheets/duvet covers (it's a bit rough on regular clothes) and making it so much quicker to line dry. Unfortunately, the people who bought our wonder wash wanted the spin dryer with it so we sold it to help pay for the haier. If we had the money I would have a spin dryer to use with a regular electric washing machine.
Edited to add: I don't know how long your washing machine runs on a single cycle, but with the haier it's only like 20 minutes, maybe 30 if I run a rinse cycle first. It would take me about 20 minutes to do a load from start to finish in the wonder wash, so I don't see it as that much time saving. And in the end it is much more hands on time than throwing it into the auto washing machine and forgetting about it.