I have a Kenwood Chef Classic, and while it does work for now, at least one tooth on an internal gear has broken off, which happened when I was mixing some pie dough. So it runs, but will sometimes skip a little. I have not been able to find the appropriate spare part.

It is also significantly less solid-feeling than a KitchenAid mixer. When/if it finally breaks, I will replace with a mixer from a professional kitchen supply store, which will be expensive, but will also hopefully last basically forever with ordinary home use.