I surrendered to the inevitable this week, and now own a Blackberry Curve. It's not yet configured for email, but that will happen on Monday, and then life as I've known it will be over.
The convenience of having email at my beck and call will be a plus, but the downside is that email will have me at its beck and call 24/7 (which it pretty much does already, so it's not that big a change). I'm making a pledge right now to leave the phone in my office during meetings, and only use it when no other source of email is readily accessible.
And having access to the Internet on a phone is pretty cool, though right now I can't really imagine that I'll be using it that much. But it might come in handy on quick trips. And the Qwerty keyboard is a big plus.