For what it's worth I have rode the 800r XP... It's a beautiful machine to ride. The ergos are fantastic, the engine is a brute, and the suspension is so confidence inspiring it actually scares me since I know I would get carried away and hurt or kill myself the first month I owned it. I hit 174 K/Hr (approx. 107+ mph) on the dreamometer! That's pure insanity to me, but with that suspension contributing to my testicular fortitude (or just plain stupidity I can't decide), I had to see where it would top out... even had some left I think... didn't have a long enough runway to find out though.
Unfortunately, I haven't had the opportunity to ride the Nytro, but from the buzz it's generating at Dootalk.com and other competitors' forums, I find it hard to believe that you will ever regret your decision.
I'm the type of person that doesn't need the fastest sled, I prefer reliability. That said, price being equal, if the Nytro competes with the new XP (even if it's not quite as fast), then sign me up Yamaha.