The iPhone lacks too many features, such as Exchange integration, also no Blackberry support.
The iPhone does work with Exchange, and Windows and Palm smartphones also lack "Blackberry support," whatever that is.
Also, the iPhone is locked to high heaven, especially to the cell networks. Not to mention its price.
So are smartphones, which are the same price as the iPhone. Unlocking them both is perfectly legal. You show me an 8GB smartphone for $600 unsubsidized anywhere, and we'll talk price.
Additionally, there aren't any MS office viewers like found on other smartphones such as Nokia, SE, Backberry, etc.
All of which, except for the upcoming version's promises, absolutely suck. You can't compose on them, and you can't make any edits without completely destroying the formatting--that's even after you go through all sorts of contortions just to be able to view a standard pleading template because of the nested tables and text areas. Business users don't use Pocket Word or Excel. A simple rich text editor like TextEdit is about all that's needed. Powerpoint would be handy if it could zoom in and out to review presentations, but because it's got a stripped down engine, it can't even properly display anything but the most basic slides. You don't have fonts, proofing tools, full formatting support, ability to manipulate charts or other embedded objects or even a way to print directly from the thing.
I suspect you think those features are more important than they are. In reality, they're nothing but a nuisance. Yes, I own a Windows Mobile smartphone, and yes, I love it. The iPhone absolutely could replace it, though. As long as it supports Salling Clicker and IM when it launches, I know a building with hundreds of professionals who will be clamoring for one.
When it comes to IM - I expect the iPhone will support AIM, but the vast majority of people use MSN ( or Blackberry messaging ).
Not in the US, they don't, but I don't see why there wouldn't be multi-protocol support for the sake of global interoperability.