the only problem they have is that the water pump likes to go out every 25,000 miles, but there are redesigned ones that remedy this problem. As with any other car (Z included) finding an unabused example is KEY in making sure the car isn't in the shop. They aren't any easier or harder on the wallet than a TTZ, whatever money you save on Nissan parts you gotta pay up for labor on the Z and whatever money you save on labor you're out for parts with the BMW.
"It's been my experience that straight-line acceleration is probably the first aspect of automotive performance that any intelligent driver gets bored with." - Peter Gregg