This was posted at slashdot, and if you wade through the normal crappy posts and jokes there, there is some good insight. One poster made a point that the tests were really geared towards being a large, single purpose server, and not a general use computer like most macs are used. They contended that the tests were specifically geared towards linux's strengths and Mac OS's weaknesses. I'm not that knowledgeable about these sorts of tests, but I find that idea interesting. I think the important thing is that the tests aren't comprehensive and should be taken with a grain of salt.