I have had one for 3 years now. The only problem I have had with it is a wire that came loose from the seat cut-off switch. Dealer sent someone out at 3:00 on a Saturday to take care of it. Other than that, NO problems. Moved plenty of dirt, cleared brush, even made forks and a snow blade to attach. I've had the rear wheels off the ground (not recommended), all with no problems. If you want one, look for one. They are good little tractors, will do much more than you could ever imagine.
About 2 years ago, I got a warrenty part in the mail. It is an extra part that ensures the loader cannot come off. This may have been what the dealer was talking about. If you look closely at the way the loader hooks on, you will see that the rear brackets resist downward and rearward forces (no way the attachment can slip that way) and the front plate takes vertical force. I think some loaders may have poped off, and JD's fix was the new bracket. What caused the loaders to pop off would be an incorrect adjustment of the front plate. That plate is controlled by the handle on the loader and that handle screws in and out to hold the front plate snugly on the tractor front mount. If this mount was out of adjustment, ie. too much play, it could spring off. This warrenty part was a bracket that ensured that no matter how out of adjustment things are, the plate would be rigidly fixed to the mount.
Don't let this scare you. If you look at a loader, you will see what I am talking about. I don't use the bracket, I just check the play in the mount as part of my walk around inspection, while I am greasing things up and checking fluid. It sounds worse than it is, and anyone that takes care of thier tractor would never have it happen to them. Just figured you should know.