Last week a colleague, who had been forced by corporate policy to switch to a Verizon Treo, donated his Blackberry Pearl 8100 to me.
It was a Cingular/ATT locked phone. I unlocked it, stuck my T-Mobile card into it, and upgraded my plan to the unlimited data plan. I the MIS department at work add an Exchange redirect of my work mail to the Blackberry-provided email address (Blackberry Enterprise Services are evil), so that I could claim a real work usage for this. But there is also a personal email on it (and you will have to ask me for that one!).
[Author Sidebar: Two days later, I managed to lose my T-Mobile Z3 Rizr. Lose. Like can't find. Likely in the hands of another happy user who has figured out the GSM thing. I am an idiot.]
What is my main purpose for this thing? I previously had not had email on my mobiles. This restricted (prevented) my ability to use services like Flickr, BrightKite, TwitPic among others. Also, I can add services such as Google Maps and other mobile apps for the Blackberry. Still waiting for Skype for the non-wifi Blackberry.
My opinion thus far is positive. While there are obviously newer and better smartphones out there now, but the Pearl meets my needs for now. And the price (donation free!) was definitely within my budget. I am still adjusting to the 3/4 QWERTY keyboard, but it is not anymore difficult than MOTO's intellitype (yeah, I know it's a stretch) system.
Will keep you updated on my joy/frustration factor.