I have owned or been responsible for about 5 of these. The #1 problem to be aware of is the poor grounding of the auxiliary 8 driver board. Basically, STTNG (and a couple of other games of that era) exceeded the number of coils that could be driven off of a WPC driver board, so they added an additional 8 driver board next to the big one. Problem is, that board is grounded by running a tiny wire to a drop target solenoid near the top of the playfield. If that wire fails (and it will), many of the coils being driven off that extra board will tend to fry themselves. From memory, most/all of the coils on the elaborate under-playfield-subway ramp are controlled off of that board along with a few flashers.

Most of the repair notes will have some suggestions for fixing this situation before it becomes a problem. I have a little pile of those light brown wrapper coils used to the control the subway diverters that say you should do what those notes say.

Otherwise it's no better/worse than other games of the era.