Just to add my .02 worth. I have never had any problems with the AWD system. It's fantastic. I've gone up 3' vertical rock faces and the fronts pull nicely. Been through nasty mud, over large rocks, etc. It's nice when you leave it in AWD and you have easy steering without having to switch it to "lock" in the 4wd when needed. I hear everybody about the engine braking system only going to the rear wheels. It was not a great system. The ADC system is light years better. That being said, the trick to going down hills is to use a little bit of gas in low gear and AWD. I've gone down 45 degree slopes this way with no issues.

 

I had a Polaris Sportsman 700 without ADC before buying my 08 Grizzly 700 and with the exception of the rear wheels sliding on steep downhill slopes, the AWD drive was seamless and I could never detect the rear wheel slippage and it worked great. I don't know how well they hold up and I am a little leery of "automatic" stuff, but my experience with AWD was good and I am sure the ADC would have cured the "problems" I experienced. Overall I do prefer the Grizzly, but not because there were problems with my Sportsman as it was a nice running and smooth riding machine with plenty of power and I never saw any sign of 3WD drive, it was either in 2WD or 4WD and the handling was good in either though a little heavier in AWD at slow speeds for some reason.