I now have over 850 hours on my X300 and have had very little trouble. It has been a very good machine and I am well pleased. The quality is there and it shows.
My only concern is the K46 transmission. I am surprised that Deere would put a transmission in a high end mower that could not be serviced without a great deal of trouble. The deck is holding up very well and pretty easy to maintain. I don't think I would buy any other brand mower than Deere.