Acually, it's just the BSD kernel. Apple is calling their compiliation, "Darwin." The look and feel, called "aqua," is based on NextStep's interface, which is still amazing.
And yes, since it's BSD, it's "real Unix..." not "fake Unix" like Linux.
I personally think it's going to be great. One of the most stable and useful OSes.
Too little, too late is not correct. Apple isn't trying to rule the world, just make money in their niche.
As for the speed limit of the G4 chips, it isn't Apple doing hardware and software thats causing it. They have little to do with chip mfg and design. What is thought to be the culprit is the Altivec enhancement, which speeds up many graphics calls, but limits the speed the chip can run stably. Supposedly, IBM has many of their G3s (IBM is not a supporter of Altivec) which run much faster.