I thought it was more of a collision between NeXT and FreeBSD. Vastly different than the old (classic) MacOS. It's a unix kernel. Very stable/solid. The first version of OS X was a bit rough around the edges, but Jaguar (10.2) and Panther (10.3) are verrrry nice. The next, major release version (Tiger - 10.4) is expected early 2005. There is a lot to love about OS X
http://www.apple.com/macosx/