I bought one for the first time last week at Sears and it worked fine on my old car (VW Jetta). It was $20 for a 6-inch model, which was about 3800 RPM of random orbits and a 1amp motor. They had 7" and 10" models but I actually like the smaller size.
For cars that really need a lot of work to get their shine back, I would recommend it. If you keep the paint in good condition and its not a big car (i.e. your Mazda3), I'm not sure its all that necessary.
I will say that the $20 model worked great. I hear of people spending over $200 for a Porter-Cable model. If you're not a professional detailer, I say save your money.
For cars that really need a lot of work to get their shine back, I would recommend it. If you keep the paint in good condition and its not a big car (i.e. your Mazda3), I'm not sure its all that necessary.
I will say that the $20 model worked great. I hear of people spending over $200 for a Porter-Cable model. If you're not a professional detailer, I say save your money.