Sometimes it says more when you look at what bad things have to say. Looking at CNN Money.com “the hidden costs of Google Apps” looks like a catchy headline, but with little substance to back it up.
Proper integration knocks out the “identity problem” as people merely log on to their company email. Single sign on makes it even smoother.
As for productivity, my first hand experience is that Google Apps is more usable “search for one”..”labelling for two” and “threading for 3″
Further our small business customers adopt it really quickly and stop raising tickets about setting up IMAP clients, synchronising mail boxes and finding archived email.