The DMD is a strange small, size. Make sure it works well before buying as tracking down a replacement can be tough. A few machines of this time period used them, but not many.
The other negative is the ball launch. If it is weak, or is hitting something, it probably needs the retro fit kit. The parts are out there, I think Marco had them all. It converts it to the better style and if I remember correctly, more like a Stern. It is a known issue on these pins. Marco may even have the parts listing on their site.
Those are the only negatives I know of.
Overall though, not a bad machine and game play. My bother in law had one, I installed the new ball launcher kit, and he recently sold it to a friend. He never had a DMD issue so that was good.