I have not checked out the Amazon Vine program or signed up, although I have heard of it and seen the icon by reviewers names on the website. Unfortunately I have a hard enough time reading and reviewing the books I already do own and that I win from LibraryThing's EarlyReviewers and elsewhere. I love to win books and it would be great to win more but additionally I am picky about what what I read and like to choose the specific books I could win.
I went to the Amazon Vine page and it indicates that it is an invitation only program...not a fan of this. EarlyReviewers seems much more fair with any permanent member able to join and "Request" to win. I wonder at times about the Amazon reviews...I think the reviewers could be influenced. I have heard in the past about writers having their friends post positive reviews on their books, although I think this was a predecessor program to Vine. Amazon Vine members definitely provide longer reviews and I like that and I think on average the reviews are fair.