I was a DOS/Windows user from 1990 up until about a month ago. Added Linux in the early 90's, but never owned a Mac until January.
OS X is *so* much more intuitive overall than Windows ever was - I got used to not having apps maximized across the monitor pretty quickly (2-3 days), and spaces has made me SO much more productive (I'm used to this in Linux, although having the shortcut keys makes it a lot easier on the Mac.)
I never use expose, although I have my scroll wheel button set to zoom out to all of my spaces, which gives a similar effect, and I'm able to see all my apps on screen.
One thing I still haven't completely gotten used to is that the mouse needs to be hovering over the application window if you want to scroll with the mouse wheel...I tend to move the mouse off to the side of the screen cos I don't want it in the way.
The biggest thing I'm trying to get used to is how to customize the OS - to put it in PC terms, what are the equivalents of editing a registry entry to add or remove a certain feature, and HOW do you find out how/where to do it? What are those com.apple.<appname>.plist files and what are they used for?
I haven't yet found a really in-depth "tips and tricks for customizing OS X" website or even book about it. If anyone has any links, that would be great
For me, I don't ever intend to switch back to windows - Vista is just awful (and one major reason I switched) and OS X is so much more secure, robust (those UNIX roots) and has a fairly small learning curve coming from windows.
-Bryan
Customise? Not much to change on a standard Mac OS X install. At most you can change the colour theme between Aqua and Graphite, colours of Finder labels, wallpaper and screensaver. [Basically the stuff you see in System Preference.] Certainly not as much to change compared to Windows, and not where near the flexibility of Linux.
The com.apple.<appname>.plist files are your preference files. They store your program settings and preference. Similar to Windows' Registry or the files under /etc in Un*x.