According to the docs, the differences:

If you are writing code that runs on both 2.x and 3.0 that needs to get tricky with tabs, these changes are a nuisance.

Even more infuriating is that the Apple documentation isn’t complete. The section ends with the sentence fragment “If you are implementing….” Yes? If I am implementing what? And what do I do if I am?

Yes, I’ve already reported documentation error. No response though. My guess is they’ll just remove the sentence fragment instead of expanding on it :(

[edited: I made a mistake in the table the first time I posted this. Should be fixed now.]