We have a 2009 M135X and a 2013 L3800 (as well as a Kubota track loader). No problems at all! Looked into trading the M series a few years ago because the newer models have a larger cab/interior but nixed the idea because of the new emission regs/DEF.
I have the 8540 and the 105X for my bigger tractors, as well as several Kubotas under 50 hp. Most are low hours, but one does have 2500 hard hours on it. They have all been excellent tractors.