I've owned 2 Polaris machines a 2001 500HO and a 2012 550 EPS, I have had minimal problems with them and use them almost exclusively for hunting. I find they are priced lower than the ones most guys promote. That being said the Yamaha Grizzly is a nice machine too.

If you are looking at used, get one with low mileage, power steering, decent tires [upgraded from stock makes a big difference], a winch on the front [front and back is a plus] and generally look it over good for evidence of hard riding [cracked frames, big dents, broken plastic].