NetBSD on m68k Macs is doing quite well. Lots of people use it, it works on most m68k Macs (I'm hard pressed to think of any on which it doesn't work), and I, for one, run it on lots of Macs. We even have a distribution which works on Macs with FPU-less LC040 processors with broken trap handling, so all of those machines which until now couldn't run any Unix (A/UX or free) can now run NetBSD just fine.

It's not going away any time soon. Aside from the compiler tools, it's actually gotten faster over time - NetBSD 5 is definitely noticeably faster than NetBSD 4. The compiler is a different story - for obvious reasons, it gets bigger and slower because of the new features and optimizations possible. But if you spend most of your time running stuff and not much compiling it, it's nothing to worry about.