Being able to use contact groups (distribution lists if you're on Windows). It is just maddening to me that I have to select all seven of my family members when I want to send them an email from any of my iOS devices. On my Mac I just type "family", and it populates all names. This seems like such a basic feature, I can't believe Steve left it out. It would seem like this would be a critical feature for use in the enterprise. I've been using the betas of iOS 5, and messenger will allow this, but mail still doesn't.