Everybody has their luck (good or bad) with quads. I see no problem with Polaris machines. My wife learned to ride on an old 2-stroke Trailboss 250. It was simple, reliable, and never gave me any trouble aside from needing a new battery and some front strut cartridges.
I just put a Scrambler 500 back together this weekend. It sat in pieces for almost a year, having survived sitting outside under a tarp and being moved to a new home twice during this time. After a good fuel system cleaning and a new battery, it started right up and runs well.
I've also had excellent luck with Wisconsin-Robin engines. Fuji Heavy Industries makes both these engines and many of the engines used in Polaris machines.