I also use Butler for another option for app switching/launching (Spotlight doesn't do this how I want it) and also to make Emacs PGUP/PGDN keys (Alt-V/Ctrl-V) work in every app. I also configured Cocoa for more Emacs-like functionality to extend the existing Emacs keyboard shortcuts it already supports. And I use BetterTouchTool to add volume up/down/mute to my mouse buttons.
That's a lot of changes to the way the default platform works, and I have grown to depend on all these modifications, but it makes OS X work more like how I want it to work, and I think that is absolutely worth doing. I wasn't really completely happy with OS X until I had these things in place. That these changes are made through 3rd party software without any horrible hacks (that I know of) makes me feel like this is extending rather than fighting.
On the otherhand, I do occasionally jailbreak my iPhone, and generally end up reverting back to stock, because that is fighting the platform.
So, yeah... Fighting the platform. Pretty much it. =]
OSX window management currently satisfies average users, but not power users. And since power users are exactly the kind of people who can do something about it, they are doing it.
Now the difference between that person and the guy thats fine with changing the windows theme to a different color....theres a distinction there the size of the grand canyon.
(Like so many labels it spans a range on a continuum, but the thresholds should be fairly intuitively obvious.)
Once I arrive in the office and sit down with two external displays, everything suddenly works against me. I don't want to use spaces (it confuses me to have 2 displays x N spaces), but Mission Control insists on the spaces bar. Putting Xcode into full screen will effectively disable the other display. I'd go insane without Divvy.