It drove me NUTS when I wanted to maximize my iTunes to fit the window I was in, only to find out that it just made it small (as shown below, which I find totally useless). I love shortcuts on my Mac and use them religiously, and figured out that you can have your iTunes window maximize (and actually fill the screen) with the following shortcut keys:

option + click on the green maximize (or +) button

Now, if we could get Safari to actually do this...