The older lasers I would agree.... There were much better builders out there. I recall the head burning up frequently on them and even to a point where many shops had the machines returned, scrapped, thrown in a corner and forgotten, etc...
As for the more recent generation... Mazak Optonics has come a long ways from what I understand and the units are far better and at the very least, up to par with other builders out there. Naturally, every machine tool and company has people who love them, hate them, and some who don't seem to care what it is.
I've been out of the laser market for too long to give you any personal POV so I'm not sure if I'm even helping you out here. What I can say is that I've heard more positive things than negative on the newer/newest models.
It's just a part..... cutter still goes round and round....