i had been working in a Masterstone 4000 for 5 years there is a problem on the spindle that you have to deal with: When the machine goes to drop or change the tools, they stuck up on the spindle and makes a really bad noise sometimes it broke the tool holder, so i had to start putting a little of grease (white, thin, and warerproof; now i dont remember the reference but it was for paper machines or something like that Mobil brand) on the cones to prevent that and cleaning it every day and replaced next day.
Also The Vacuum pump sucks it came with a plastic elbows on the valves, leaks the preassure out so i had to switch all of them. beside that they use the same vacuun line for the suction cup to table and the suction cup to piece so leaks at hell. (piece movemet guaranteed).
Intermac correct most of this problems on the Master 33 the one i am using rigth now, it is a pretty decent machine no problems at all. (in 2 years)
The Master 4000 it is not a bad machine all depends on the amount of money you paid for it. ( also remember it is not an opent top so is a really pain to load and unload..)