YMMV, but my E46 BMW has been very reliable compared to an RX-8 bought at the same time. Audi was still in the process of applying the lessons of the RS4 to their everyday cars, but I still wouldn't call the RX-8 reliable compared to its peers. As you hinted, there are a couple of problems that lead to full rebuilds before 150k miles.
* Underspec'd the ignition coils
* Didn't do enough on-road reliability testing
* Lowered the oil pressure and removed OMP ports
* Designed the oil filler breather in a way that allowed oil into the intake
In '04, the first wave of RX8s were coming in to the dealerships after 30k with severe misfire from the coils going bad. Mazda didn't have this failure mode in their factory service manual, so the cars got replacement engines (poorly reman'd in Mexico, not made on the Mazda Japan line). These didn't last because of poor manufacturing. Once the coil issue was figured out, the 8 became much more predictable and reliable.
As noted by Busterarm, they fully got their act together with the series 2 update.
[I own an '04 RX8 with ~130k miles)
Pull and rebuild is pretty easy though.
http://www.allpar.com/mopar/turbine.html
It was not, in the end, a production car, but there was a lot of data gathered as to performance and reliability in real-world settings.
Not too long ago, Jaguar had a concept CX-75, which was a hybrid mid-engined supercar where the piston engine was replaced with two Bladon Jets micro gas turbines. After 2008, they didn't want to commit to an expensive limited production vehicle, too bad.
https://www.theengineer.co.uk/issues/18-october-2010/jet-pow...