One of my biggest pet peeves with Mac OS X is it's non-conformance to Focus Follows Mouse. Why can't Apple fix that for fucks sake?
Because Apple shows you the only way (or the highway).
For novice users, I think it is a pretty good O/S. For semi-advanced users, there are traps in the making. For power users, aside from the FFM issue, in my experience, I have been happy with it (after doing some tweaks like macports and some UI customizations). http://www.macosxtips.co.uk/geeklets/collections/dark-is-beautiful-1/