I picked it up last wednesday. I only got to put 20 miles on it due to the weather but hopefully I will have the needed 200 miles for the break in. Though I haven't put it to the bar yet or gone through any serious mud this thing has impressed me. I picked it up Wednesday and put the tires (gators) on Friday. These tires are probably the most under estimated tires out there. They are even more aggressive then I expected.
The bike has great acceleration, super power,and rides like a dream. I am fortunate to be able to ride this one and ride the 600 grizz consectively since I own the both.
The 660 has a much smoother acceleration then the 600. I think the 600 was aimed more for the utility side then the 660.
I have to think (IMO) that this is the best looking ATV out there. I hope to get some pics soon. I need to reload the scanner on my inlaws computer since I can't find the driver to make it compatible with XP.

 

Yes, you are right the new Griz is even more awesome than the 1st generation Griz. The 600 Griz is more utility oriented but, you have to remember, The design is 4 years old. When it was new in 98 it was best ATV of the year. Since then everybody has been gunning for the griz. It has been outclassed by some of the newer big bores including the new Griz. It 's still a hoss though and will still kick 95% of the utility atv's butts that are out there without sweating hard.