Turtle,
I just bought an '06 400, my brother rides an '02 400, and a hunting buddy has a '05 400. Between the three of us, we havan't had any problems at all with our Arctic cat's. We primarily use tham for hunting in the winters, but we ride them pretty hard in the summer months for play. Some of the things I really like about my 400 is the digital display speedo, under seat mounted fuel tank, reliability, fuel capacity, and I think that the AC's have the best ride around, thanks to the best independent suspension in the quad market today. I don't think you could go wrong with the AC....
Good luck!!!
Longshot