Something to keep in mind about them is that there is no CPU, or TRUE ROM chips, on them.
The entire game is contained on a series of logic boards.
From what I've heard, the wiring connecting it all looks like a huge rat's nest.
The ramification of that is that, if something goes wrong with it, troubleshooting can be a really BIG pain.
On the other hand, it has yet to be FULLY emulated, IIRC; and will probably NEVER be re-released in MAME, so this may be your only chance to get that particular game.