I used to use it but it never got a clean enough dry, having a black car makes it everything show up though. I ruined a filter too by using a different soap, so I ended up not buying any more filters. I still use the unit itself, I love being able to soap from the unit and get a good spray. I guess it was worth the unit for me.
I bought one a year ago, same time as I bought my new Focus. It has worked great, no water spots whatsoever. I also enjoy the fact that the final rinse is electrically low or non-conductive - I feel much better about rinsing the engine compartment.
Shop around - I have found the filters and the soap for around $4 each at local discount shops. I change the filters when they turn a darker brown, compare with a new one sometime. Five or six complete washes easily.
Today I washed my car w/o using the Mr Clean soap. I used Mequiar Gold Classic. I did use the Autodry final filtered rinse. As always the car dried spotless, but as focusin mentioned in an earlier post, the glass had no weird film from the soap.