One nice new feature in Outlook 2010 is that if you get, e.g., a Word attachment in an email message, when you click on it (just click, not double-click), it will open that attachment within Outlook itself. That is, it doesn’t launch an external instance of Word, it just displays it in a ‘previewer’. It also works with Excel (I don’t know what other types of attachments it works with, those are the only ones I’ve tested).
Does this cure cancer? No, of course not. But it is a nice feature.