title: Creating new UIWindows, taking over key window -- bad practice?
body: <p>I'm working on an app which needs to display an overlay an top of everything else. It does this by creating a new UIWindow, and using makeKeyAndVisble to "take over" the screen. When it's done, it gives control back back to the original UIWindow.</p>
  
  <p>Is this a bad thing to do?  It feels like it's taking control of the app at a low level, which is generally bad;  on the other hand, it's very straightforward to do, so maybe it's perfectly acceptable.</p>
  
  <p>Opinions/experiences?</p>