Librarything done and dusted. As others have mentioned a useful social tool to connect readers with other readers if it could be integrated into public library catalogues. I entered a bookshelf
of Doc Savage's library to test LibraryThing and it was easy to use although I needed to add some other resources to find bibliographic information for some older, obscure editions. I searched by ISBN because I wanted to record the actual edition I owned and this worked reasonably well . Tagging is an interesting concept and useful for a personal library, although I am not sure how well it works in larger groups. However I think the mixture of controlled vocabulary subject headings and the more spontaneous and common-language tags is the way of the future.
Librarything is fairly flexible in how it displays records and gives users the oportunity to change display formats. Subject headings generated even from Amazon seem reasonably accurate.
Librarything is still in it's Beta stage and seemed a little slow at times but I think this may ahve been a combination of my slow web connection and some problems the site was having at the time
I have also added the randomiser widgit to my blog to generated titles from my library.