I bought my first pro 600 5 years ago, I used it mostly for frosting, and a little cake mixing and cookies. but last year it started to fail, the speed would go crazy, even set on #4 it would go very fast and the motor would overheat and the mixer would turn off. I think it was due to lots of powdered sugar flying in the air. But in December I changed the speed control electronic board and the sensor and it is working just fine. I bought the replacement parts also in Amazon.
And since I have an old KA 4.5 qt mixer (12 years) I decided to retire her and bought my second pro 600, the empire red was about $240.-
I really love them, I couldn't bake without them. Maybe some of the bad reviews are from people who don't know how to operate the mixers.
Good luck with yours!!