I have been an LT user for a few years now. I am totally dependent on it to keep track of my reading (especially when the novels are in series) and also to hold my wishlist.
It's social enough for me, and I find the user base to be extremely knowledgeable and helpful. I also love all the statistical data that is made available throughout the many subsections of the site. The interface is not especially intuitive, but you get out of it what you put into it.
I don't mind paying to help out all the cool community projects that they do. You all should check out the "Legacy Library" page, a database of the libraries of famous minds. (I share 12 books with Ernest Hemingway).
http://www.librarything.com/wiki/ind...eted_libraries
Somebody earlier in the thread asked whether there was a mobile site. There is a little bitty one, just to access your own library at:
http://www.librarything.com/m/