Oddly, Microsoft used to be app centric and moved to being file centric with Windows 95. The idea being that you cared less about the app and more about the document you were using. Apple is going back and saying you care about the app as the dominant focus.

This is interesting. For example, my mom knows the document she wants to open is her 2009 tax return document. The fact that it is a PDF or she reads it with Adobe Reader -- I'm fairly certain she doesn't know. If I were to layout every application she has installed and told her to find the one to open to access her tax documents I honestly don't think she'd have a clue. She'd probably try Word. I suspect she's not alone on this.