According to who?
edit: While I'm fairly certain this post isn't, it certainly smells of trolling.
Anyway, this discussion is pointless, has been repeated countless times before and will not end in agreement.
Is it sufficient to say that a good reason I use my Macbook with os x is because it makes me happy?
Because I was tired of Windows, and when it came right down to it everything I choose to use as a developer is platform-agnostic and generally easier to install on Darwin.
And it's pretty.
Edit: sorry, seems I was wrong :-)
(FreeBSD user-space utilities, with a FreeBSD/Mach hybrid kernel.)
Of course, in today's web 2.0 world, the OS core is not so important: more people are building web apps rather than desktop apps.
i spend a lot of time writing server apps, some of which serve up data for web clients, all of which are ultimately deployed on linux/unix. the low-level apis available on a mac are pretty close to identical to what's available on linux, so it's easy for me to do development and testing on a mac.
i don't know why i'm bothering. it's pretty clear you've already made up your mind, so why even ask anybody else.