The first thing I’ve learned is CoCaCl:
Cocoa applications are written for X and take full advantage of it.
Carbon applications are written for 9 and X — work OK, but Cocoa is better.
Classic applications are third-rate. X runs emulation software pretending to be 9 and these apps run within that. It’s like using Virtual PC to run Windows 98 on your Mac.
I’m hoping that many of my applications will run just fine.