I got my first Blackberry last week and am hooked. My communication needs over the years have changed such that I have an increased dependence on data connectivity when away from home. Sure, a lot of that dependence is psychological, but that's for another story...
Anyhow, after evaluating a number of different devices, the Blackberry struck me as being the best fit. I liked the feature set of Cingular's Ogo, but the device itself was obviously marketed for a different audience and the lack of voice capability in the current model would force me to continue carrying two devices. My Sprint PCS phone offered great data access at a reasonable price, but even with the efficiency of predictive input and the speed of the 1xRTT data network, working with text messaging and e-mails from the phone proved tedious-- though it was how I've done things for the last few years. I also contemplated a smartphone, either a Treo or a Windows-based device. While price-wise they were comparable, they are intended as a more general-purpose device, while the Blackberry is focused on the biggest thing I needed: the instant gratification of immediate message delivery.
I am using the Blackberry 7250 on Sprint PCS. As a manager of a Sprint PCS retail location I was able to work the system a little bit and get my hands on this hard-to-procure device, and it has been worth every bit of the trouble I went through to get it.
My Blackberry was meant to be a predominantly personal device, but it has worked its way into my business functions already. My @sprintpcs.com e-mail address I've always provided to my customers now automatically forwards copies of incoming messages to my Blackberry, so I can get back to them even faster (and I have auto-BCC configured so I have an archive of whatever I send them). I am keeping track of customer contact information in my BB and setting reminders to call them back to follow-up on purchases and other interactions. And I'm now slighly less forgetful at work, too.
Blackberries definitely have a place in the personal market. Unfortunately, I know of several providers that are reluctant to sell them to individual consumers (Sprint PCS is rumored to be planning a retail launch, possibly including consumers, in September). If you do decide to pursue one, the 7250 seems to be a great unit. Do some research though, as every Blackberry has slightly different capabilities... and even the same model may work differently across different providers--- research the limitations on Alltel's 7250, for example.
The montly data cost can be hard for some people to swallow, but that's for you to decide. For me, Sprint's $45 all-you-can-eat Blackberry plan is a bill I don't mind paying.
So go get one. You'll be glad you did.