I just had mine rebuilt. The clutch side cylinder got ruined when one of the rings came apart and got thrown around inside the cylinder. New Wiseco pistons and rings, bored cylinders and $500 later, its like new. I heard some stories of the 550 Fuji fan having issues, but I have been reassured by several Polaris mechanics that they only had a few years with oil line issues and cylinder lining problems, neither of which affected the 2001 models.
Hope to get another 4-5000 miles out of it. I only ride it locally, so it only gets about 1,000 miles per year at the most (depending upon the snow here). As mentioned, it is the EASIEST sled to ride. Easy to steer, goes where you point it, rides well for a traditional sled, and very light. I bought it not only for me, but for my GF who has never ridden a snowmobile and her kids, who also have never ridden a sled.