have a 2001 9650W machine and am well pleased. As far as I know there is little difference between years rather than they have started using soybeans someway in the outer plastic shields ,covers etc.
Somewhere on the John Deere website they list each model year and the improvemnets that have been made to them. I think it is under the custom harvestors section.
There are some changes to the grain tank area. The roll bar structure in the grain tank that supported the unloading auger is gone. It has been replaced with a bearing and support shelf, much like the STS. Makes it a lot easier to get into the tank and move around, put up the extensions, and to clean out the tank.