I have 2 x Star Trek Next Gens and i will keep both to the day i fall off the planet.

STNG is a great looking game and extremely fun to play.The audio is great and the playfield lights are excellent.
The widebody of STNG shows the engineering excellence of Williams.The missions are many and the different ramp shots, 3 flippers, and the various targets and sink holes make the game both fun and challenging.Parts are easily avail including cliffys etc etc.

Maintainence is straight forward if u have a manual.Good Pinball techs know these machines back to front.
Just buy a good example from a decent collector or a well known dealer, with a 30 day dealer warranty, so that u know the machine has been shopped properly.
If u like Star Trek you will LOVE this machine.If u are not fussed about Star Trek u will still LOVE this machine,  BUT if u u hate star trek, then the machine will never appeal.

I have never seen anyone who was positive about Star Trek play a Next Gen and walk away unhappy.