Several months ago I switched from the Blackberry to the iPhone and the results have not been great. When my blackberry received an email, phone call, sms, messenger, it would always show up in one place making it easier to reply. The lack of this feature in the iPhone has definatly effected my response time which is not good for business.
Now with the release of iOS5 and the Notification Center i will be back in business.
Apple has made this release available to developers and of course the jail breakers are busy figuring out how to get the release to you early. My advise is to wait for the official release as it should be around the corner.