Pros: Convenient. I can wash my car every day of the week since I signed up for the monthly plan. I get a wax spray along with the regular wash and a little car freshner for $18 / month. It's close to my work.
Quick. It's a quick wash and I've never had to wait in line yet.
Cheap. I dig the price. I would pay $8 for a one time wash at another place.
Cons: It's a three minute wash. So don't expect your car to come out looking like it just rolled off the showroom. I still have little bugs and things on my car after a wash but it gets dirt off and I can just go back tomorrow.
I gotta work the inside. Not a big deal.