Timely reality check from my Burton Group colleague Guy Creese; see the link below for more details
Out of the box, this application has a much more of an enterprise attitude than the recently announced Google Apps, Premier Edition. ContentExchange supports workflow, versioning, tagging, and the ability to subscribe to RSS feeds about documents. In fact, this solution displays an early version of what I call "content analytics," in that it displays usage information about the content as a way for users and the enterprise to decide what's important. Google Apps has access to this information behind the scenes, but does nothing with it.