Unless Apple partners more with Microsoft to get access to Mobile Device Manager or gasp Blackberry to be a BES capable device you will not see iPhone adopted in large enterprise that have strict security concerns. We initially supported it but due to encryption regulations and the need to archive and review SMS messages (both are not available on iPhone) we have sense suspended any additional iPhone users and those that stay on the device are limited to Web access email / PIM only.
Blackberry is the standard to which any other device will be judged in enterprise. It's the gold standard and has all the management one would want when having to support mobility. I think they have made great strides in consumer adoption and their marketing and newer devices reflect that.
iPhone to me is the evolving iPod family and the biggest seller lately seems to be the Touch. Blackberry is the evolving phone .. really two different segments that are bleeding into each other but each have weaknesses.
I use both and iPhone is a great weekend device when I want to look up things, listen to music etc. Blackberry is day to day get work done device.
WinMo is pretty much dead. I still get the latest models from our carrier partners and it's a mess how in all these years they can't make a usable device.