I have it as well, and it works fairly well. However, we have hard water here so it will leave a slight bit of residue (a very fine powder), usually in rings around wherever there may have been larger spots of water. It's easier to get rid of that with a car duster than to hand-dry the whole thing.

What I like most is the soap they sell for use with it - your wash mitt really will be a lot dirtier than usual when you use it. I don't know if you HAVE to use theirs or not, but it is better than anything else I've used in the past. They need to sell it in a big container like Blue Coral or pretty much any of the other car wash liquid soaps out there do.

Anyway, I used the system as prescribed for a while but got tired of needing new filters and soap all the time, which was pretty regularly since I wash it often and we have hard water. I just went back to hand-drying with a good synthetic chamois. It's cheaper and I never have really minded doing it. This thing is kinda like printers - where they get you is with selling you the cartridges afterward.