The only mechanical problem I can think of off-hand is that they had alot of problems with the power supplies in them.
The art, and the Tron specific pieces (monitor shroud, black lights, etc...), are the big things with them.
Everything on them is replaceable....for a price.
The question is, how many things are you going to have to pay to replace, rather than just buying a restored/better condition one to start with?