As far as how this sled goes, I just spent 2 days at 4-7000' riding in 2 1/2 to 3' of powder boondocking with a bunch of 800's and I had NO TROUBLE going where they did. The sled was a little doggy the 1st 5 Hrs but after that it rips. It has wicked throttle response, BEST I have ever seen on a stock sled. Now if your going to climb big shoots or even big hills in deep snow, it is just a 650 and does not have the torque of an 800. But with all the efficiencies Polaris did to this thing like the 2.75 track and belt drive, great chassi, lighter sled then other brands and a square bore and stroke motor, it's crazy GOOD!!!!! Just so you know this is my 1st Polaris since 1994 XLT so this is NOT a Brand loyal opinion. Been riding Cats, Doos and Yamy's up till this sled.
To give you an idea of the ZIP this thing has, Me and a 800 18' Cat with a 153x3 (this sled is not stock, has some goodies, it used to be mine) and a 21' 800 Alpha 165x3 with a can, reeds and a belt drive lined up twice on the groomed trail back to the truck and my old Cat and my new 650 bumped skis to 75mph (thats when we shut down), and the Alpha was 2-3 sled lengths behind. Last couple days I have been doing some teaks to it and it is pulling harder now. Might just surprise some 8's out there...............