I started using twitter some 3 months ago after reading the book from Tim O'Reilly about twitter. In the beginning I also thought how useful a media can be by limiting your messages to 140 characters. Then I found interesting accounts to follow e.g. the local train station that twitters departure times and delays or e.g. I follow Tim O'Reilly and noticing about the eBook of the day made me save a lot of money in the last months when buying eBooks.
I also get reminded about local activities like the weekly market or events that are scheduled for the weekend. I can even get support for my mobile phone from the telephone provider or from BlackberryHelp. So twitter became really useful in this period. And of course I also follow lwnnet. :-)