I have had a number of issues with my 2000 base boxster, which now has 84K on the clock. But almost all of them were a result of me mucking around with the car, ECU chip, exhaust, intake that sort of thing.
The only thing that comes to mind was that comes under the heading of a reliability issue is that a bolt fell off the transmission housing and I started spilling tranny fluid. I noticed this black trail of fluid that followed me down the street into my driveway.
I thought my tranny was toast and took the car to the shop and saw the bolt was missing and was still sitting on the plastic undertray, they topped off the fluid and put the bolt back in, no problems since. So I would say no issues with engine or drivetrain for 84K and the sucker runs like a top. BTW, I change plugs, oil, and clean the air filter very regularly.
Ed
