I never thought of Twitter as a microblog until I did this week in web 2.1. I always aligned it with Facebook and considered it a 'status' update-which in my mind was different to a blog, although now I see where the lines are crossing.
I have signed up for twitter, but I don't think it is something I will use because I don't like the character restrictions. Also in relation to the character restriction; I found it difficult to understand what some messages were saying. So far... not a fan of microblogging!
I can see libraries making use of twitter for events updates, new book release notifications and public announcements but I think the character restriction could make relaying information difficult to understand for some library user groups.