I have a fondness for full-screen windows, which means that Alt-Tab (in any environment I'm playing in - don't know what the OSX options are, don't get a chance to play there) or some form of pager or taskbar is how I navigate between programs. And I have an almost irrational need to minimise/hide a window I'm finished with so that I know it's out of the way, instead of lurking ready to unexpectedly be there and take an unwanted mouse-click when I'm least expecting it.
This is just one of the numerous good reasons I have for my intense loathing of programs that (are allowed to) jump up and steal focus, obscuring what I was concentrating on and receiving seventeen key clicks before my brain catches up with first my eyes and then my hands.
One consequence, however, is that I will ask for a program to open, jump to another program to check on something while waiting for program1 to respond, wonder where it got to and, if I'm on WindowsXP at work, hit Windows-M to minimise all windows and display the desktop.
Here's where it gets entertaining. Warning or dialogue boxes don't get a taskbar entry, so you don't know they're there. And if I hit Windows-M when a box is sitting waiting for action (press OK or enter a password, usually), I don't get to see it. So I try and open the same program again, which does nothing, because I haven't responded to it yet.
So I have to use Alt-Tab to see if there's a dialogue box I don't know about...
Which quickly becomes annoying. Then graduates to infuriating.