I have an old Wrestlefest cabinet that I put a JPAC in years ago. I must have been one of the first people to buy a JPAC, I believe I ordered one the day Andy released them.
Anyway, I never disconnected the power supply because it ran the coin door lights and I didn't want to rewire the cab to get the power from the PC power supply because I needed to keep that PC portable. Well, that cabinet has been just fine ever since and it's at my brother's house, who plays the cab daily. Never had a problem with the power supply or the JPAC, both have been fine since day 1.