I rode the prototype Nytro in spring '07 and was amazed. My sled then was an '05 Rev 800, and the Nytro felt better in every aspect. I bought one that fall, traded in my Rev for it. I was INCREDIBLY disappointed with the production model as compared to the prototype I rode earlier. The power was down, the suspension sucked royally (I remember getting buried in the flats once when nobody else in my group did), etc etc. Once I spent over $2k on a Timbersled skid and Polaris 5.1 track, and clutching mods, the second season was a LOT better....I rarely got stuck and was happy riding it, until I rode my friends' sleds. I now own a '12 Pro RMK and aside from shocks (I'm 250# with gear) it's 100% stock, and I absolutely love it. I love Yamaha build quality, but until they produce a "production" mountain sled that performs out of the box, they'll not be getting my money again.
I was scared to death of going over 50 mph on the trails with that Nytro, such a twitchy front end and top heavy feel. I put 1100 miles on it and found that my friends were hesitant to ride with me the first year, always having to dig me out with that heavy sled. 2nd year was better, but I was worn out after a day of riding. Steep sidehilling was a gamble, because once it started to lean downhill it was over.
I'd love to see Yamaha come out with a laid down 4s motor to keep the weight low, improve the oil tank reservoir so that you don't lose all your oil if you find yourself inverted, lighten up the chassis and build a powerplant that actually can compete with the 800 2s, without boost. Or, and this is really reaching, develop an 800 2s motor with their DI technology in a competitive chassis........I know, never gonna happen, but I can dream!
Until then, it's 2 strokes for me, which means anything but Yamaha.....I lost 2 good years of riding and thousands of $ on that Nytro......