I have had a Stihl Magnum for 15 years and it has never missed a beat. It gets used heaps.
I have a smaller Stihl 180 i use for camping, and it runs great, i did have a problem with the throtle, where the wire was slipping off, took it back and they changed the throtle wire with a different one becouse they were having problems with them, all good now. and they are a cheap saw.