I'm unfamiliar with "object-C", but the "official" language for MacOS X is "Objective C". Could this be the same thing? Doesn't matter to me, I'm still in the C/C++ world, though I program under MacOS 9 and X every day at work. I'd guess that it's changed less than you think.
I'll have to say that I'm VERY impressed with what Apple has done with OS X. They've taken NeXT and merged it with FreeBSD and built a GUI layer on top of it. Crazy stuff that. =)
If I understand correctly, Steve Jobs was more or less heading up NeXT and brought that to Apple with him when he went back.
And to keep this on topic, check out
http://www.emulation.net for a MAME frontend. That's AFAIK the best mac emulation site.