Its easier to change the plugs on an FTO compared to a supra. The inlet manifold has to come off, and that's it, very much like the NA supra.
The non mivec gr engine is more reliable than the mivec. There loads on the Mivecs letting go, but very little on the non. The GR model also has hydraulic tappets, so no need to adjust, whereas the mivec needs them fettling every so often to shut them up.
The only reliability issue I had with mine, was due to a previous owner steam cleaning the engine bay, forcing water into one of the big multiplugs on the gearbox, this messed the gearchange up and was stuck in learn mode. I found the fault, replaced the loom, job done.
The only other thing is as Abs says, they're noisy compared to other cars, especially tyre noise.
Oh, your biggest problem will be Mitsi themselves......they're useless.