There have been 64-bit processors around for a long time. Remember the Alpha? Sparc? MIPS? PA-RISC? Itanium? Apple brought out the IBM's Power4-derived PPC-970 (aka G5) just after amd released the Opteron. Despite apple's claims, it odesn't quite beat high-end PCs overall, but it is a fairly good step overall. I'd be interested to see a power5 based version wth SMT. So the hardware isn't really ahead of PCs, after all there are 64-bit PCs, and there have been 64-bit workstations for a long time. Also, don't forget that simply being 64-bit doesn't buy you any extra performance unless you need to address more ram, or you need to use 64-bit ints.
As for the OS being 64-bit and functional far before windows, that is mainly a driver issue. Apple controls the hardware, they don't have as many drivers to write, and they have the resiurces to write them. OSX is mostly based off of BSD (although there are many chnges in how it works), which has been a good OS for a long time now. I don't really like what apple has done to it, however. And their UI really annoys me. What was my point again?