This is clearly anecdotal, but of all the mac users I know (and that's a lot), only one has a bb (and it's because it's work-issued and he's cheap). So that's why I'm surprised.
This is also anecdotal, but: I've had an original iPhone and an iPhone 3G. I'm a die-hard Mac user. I've been using and developing for OSX since it was called NeXTStep. I have an iPod Touch (original release) and I love it. As a multimedia device's OS, the "iPhone OS" is perfect and a joy to use.
I do not, however, love the iPhone. Indeed I hated it's ridiculously short battery life and the awkwardness of typing on a software-keyboard. Apple's refusal to allow background apps is asinine and the iPhone 3.0's "push-notification" system is a very miserable substitute because it only works when you're connected to a network - and in my line of work, that's frequently not the case. (Closer to home: what if I want to run a background app while I'm on an airplane with the iPhone in Airplane Mode? No joy.) A common file-saving area so that you can share files between applications? Nope, sorry, not provided.
Not to mention that the iPhone's interface paradigm involves you dragging your finger through a smear of ear grease.
Though it seems great at first glance, the iPhone is, upon closer inspection, a rather badly-designed platform. It might play music and flip photographs when you rotate the device, it might even be great at playing games, but as a working device it's miserable. Completely useless.
One day I was driving back from France and I found myself switching the phone off after every conversation because it was burning through battery life like nobody's business. I thought to myself "this is ridiculous... what if I get stuck somewhere and I don't even have enough battery power to call someone? What if somebody needs to call me and can't reach me because my phone is off to preserve power?" I called Apple and complained. They told me to switch off 3G (which I had, incidentally; but then again, what's the point of touting hardware functionality that needs to be shut down to preserve power?) and to switch off Bluetooth (I was driving! It's quite sensibly an offence to drive with a phone pressed to your face!). Beyond that, Apple was adamant everything was peachy and normal.
I hung up the phone and thought "screw this". The next day I wondered into my office, defeated, and asked to be issued that BlackBerry Bold I'd been offered so often but had always declined.
I love it to bits. It has a good keyboard, an integrated interface, a bright screen. Best of all, it's a good phone, and offers excellent battery life even when running on 3G with Bluetooth enabled. It holds a signal far more successfully than my iPhone 3G ever did, from exactly the same places - I can finally make and receive calls from my bedroom, where my erstwhile iPhone regularly fell off the net.
I've been constantly frustrated by the difficulty of synching my BlackBerry to my Mac. PocketMac and Missing Sync raped my contacts and calendars. Routing through Google with Google Sync and Spanning Sync is a constant affliction, my contacts are regularly mangled. I've been on my knees praying for a BlackBerry iSync plugin. No matter. This software from RIM will do fine. It's exactly what I needed. I can't wait.