Pros
The pay is pretty good for the work in my opinion, and you don't have to deal with the public very much. You just prep/dry their car and send them on their way (most of the time). You can control how many hours you want and your availability is understood. You get a tan (but that might be a con, because it's a farmer's tan). The tips are pretty good if you get the tips at your location. The other employees that I've worked with steadily have been good people. My manager is a great guy, and manages the location well.
Cons
The upper management can be overbearing and sometimes have exceptionally high expectations. The heat during the summer months can be pretty extreme. Use lots of sunscreen. You are lucky if you get to take a break during your shift, but you're kept busy so you don't really notice. In my experience, there is a lot of people coming and going, and some of them aren't good workers. So, you have to make up for their laziness or lack of work ethic.