This article is rather ridiculously long, but it's a very very good and thorough comparison between OS X and BeOS. I followed the BeOS practically from its beginning, and I've always admired it from a distance. It's a little depressing to see even its supporters bailing out.
This quote from the article sums it up very nicely: "This is all very simple. I'm going to jump up and down and whoop about OS X, and then I'm going to bitch and moan like nobody's business."