It's interesting. For the little I have seen (and I was only able to give it a quick glance) it includes syntactic support for multi-threading being built into their Objective-C compiler.
Chris Lattner's first paragraph here talks about that a bit, although it doesn't give a timeframe for when the gcc implementation will make its way back to the main distribution:
Although, there's a comment by Johannes Fortmann here that says that the code has been available in an svn repository since at least September 5, 2008:
Sure. I'm not trying to say that Windows was ahead of its time, but rather that Apple seems to be making a big deal out of a feature I'm kind of shocked they didn't already have.