Ive never used a Blackberry, could an evangelist tell me what the Bb does that makes it so amazing for email as I have difficulty imagining exactly how it is so far ahead of the other devices.
proper keyboard on the decent ones, at least as reliable as an iPhone in the case of the hansets, far more suitable for enterprise users. The security is also far better than just using plain exchange, right down to little features like 10 incorrect password entries (Can be adjusted) will reset the handset. You can also apply permissions remotely, so you can have someone able to receive e-mail, but not send if you so chose (which does have some uses oddly enough). Basically with a Blackberry alongside BES you are buying security and reliability with a trusted solution. Also free handsets is a HUGE draw to an enterprise, and its been around so long that pretty much any business that wants mobile e-mail already has BES, and they have zero incentive to buy the iPhone.
Edit :: on a side note, i wouldnt have one myself. Outside of a business they have little use except for people to wave them around like they are important, much like the iPhone in that respect.