I deeply respect Apple for its attention to user experience and design, but I don't agree with all of it's choices they make for me. I wish there were many different Apples, then I could choose the one I like, but unfortunately we have only one.
In my very limited encounters with OS X's desktop environment, I didn't find it practical, and the proposition is: take it or leave it, right? Changes to the default desktop environment are as outlawed as they are in Windows, or aren't they?
I maintained an xmonad environment for a couple of years on various versions of ubuntu and switched to osx last year. I share your view that Apple frequently makes choices that don't map to my expectations of an OS.
I use slate + pckeyboardhack + keyremap4mac to control my windows via keyboard. Instead of using multiple monitors I switched to a single larger one which is easier to control.
I guess my point is that you can kind of change things, but you might need to compromise in some areas. I don't know of a way to get multiple desktops, for example, but I can switch between apps by binding keys to names of them and get around that way.
It's also going to be hard to try these sorts of things out in the store, and given how expensive the devices are it's difficult to justify given you may end up with an expensive tool you don't want to use.
I'm not quite sure how outlawed they are in windows, but I've replaced the alt-tab/cmd-tab with Witch by manytricks, to make it more windows like. But something like XMonad, while it runs, only affects X apps, and is not quite so useful.
In my very limited encounters with OS X's desktop environment, I didn't find it practical, and the proposition is: take it or leave it, right? Changes to the default desktop environment are as outlawed as they are in Windows, or aren't they?