All similarities of Twitter is Available over FormSpring.Me like changing Themes, Following button, Profile Pic, Uploaded background but the working is not at all like microblogging. After the increase of Twitter lovers, there many new microblogging site launched like identi.ca and others but they didn't gained much popularity coz these all are the same concept and works same!
I must say you that formspring is very different from the Twitter service and is totally works on different concept. It is a site where users can ask their question to any users registered and the user can answer their question without emailing him.
To grab his answers, he need to come to that profile page later to see his Answers along with the Question Publicly!
FormSpring is too having a Widget to put it on your blog, where the users can ask question to you directly from the sidebar without visiting the contact page. I suggest you to try this site once and i am sure that if you like Twitter then you enjoy this site! :)