90% of your time is spent IN the email app. Not the boot process, nor the home screen and certainly not the IT administrative process of setting up servers (users do not care about that -- that is why highly paid IT people deal with it at Enterprises).
As a frontline helpdesk worker at a corporation that deployed hundreds of Blackberrys, I can assure you that the users frequently cared a great deal about the crappy UI of the Blackberry OS. When I left, the MIS (yes, we were that old-school) department were beginning to research moving away from RIM because their end-user devices were consuming too much of our helpdesk resources. And because the executives, who all had iPhones, came to us and asked the question why we couldn't provide them a solution that worked as well as an iPhone's email.