Leopard's plenty flexible. By choice, do you mean being forced to pay extra money just to get an operating system that hasn't had features removed? Because I know Leopard only costs $80, but it's full-featured and that's what I care about.
Or do you mean the choice to tinker with every little aspect of your computer? Because the system's entirely moddable. I mean, I would never voluntarily hack my computer, because I cherish it the way it is, but I remember there being a lot of buzz about the Gaia Suite, which is a complete redesign of the OS.
Do you mean the lack of programs available? Because you can get MS Office if you really don't like iWork (though iWork is wonderful, in this user's opinion), and you can get replacements for every single iLife program. It's just that most people don't, because iPhoto and iTunes and Mail and GarageBand are really all excellent programs. (The one program on my entire system that I dislike is iDVD, and I feel like one bad program is a small concession to make.)
If by "flexibility" you mean a non-unified system, then you might have a point, but I like knowing that the same keyboard shortcuts work for every single application I have. I like knowing the menus work the same. Hell, I like having a system-wide spellcheck. You've still got choice - I'm sure you could make a new spellchecker - but really, what's the point if it works?
If you're going to diss an operating system in a community of people who really are enthusiastic about the computers that they use, at least make a good point, like the guy who mentioned Apple's Java fark-up. You can't come in blindly making insults and expect anything good to come of it. So how about you come up with some good criticisms, and in return I will try to be fairly critical of your operating system in return.