i started with library thing and moved to Shelfari, which i still use. i have also embedded shelfari on my home page for school. i have friends that use goodreads and i am looking at the differences. what i can tell so far is that it is an individual preference. you can use many features or only a few. Shelfari meets my needs for now.
Took a look at the other sites, nothing exciting.
i love listening to books on tape, but reading a book on my phone does not interest me at all. The print is so small.
i liked the idea behind the one minute critic, for video book reviews