Windows phone does this unification in a way that works better for me.

All messages (sms, chat, facebook messages) are together All emails are together All social walls (facebook, twitter, linkedin, etc) are together.

You can switch the communication medium i.e. reply to facebook message with an SMS and so on. Of course all of these are filterable and configurable. This seems to work better for me as they are most of the times distinct worlds.