Saw one today as I was paying for my 06 yfz 450 valve adjustment(they were still in spec). Very sharp quad! I haven't read or heard anything about them and I don't need to buy one as my 06 is still in cherry condition. However, they are sharp and if they are whooping azz I may reconsider.

 

I have heard they are very nice machines but the older ones such as the ones you have are actually faster and the motor seems to have more power but this is just what i have heard but i dont know anyone who has one to ask them about it