The Amazon reviewing process is through what they call Vine Customer Review of Free Product, which they describe as follows:
"Amazon Vine invites the most trusted reviewers on Amazon to post opinions about new and pre-release items to help their fellow customers make informed purchase decisions. Amazon invites customers to become Vine Voices based on their reviewer rank, which is a reflection of the quality and helpfulness of their reviews as judged by other Amazon customers. Amazon provides Vine members with free products that have been submitted to the program by participating vendors. Vine reviews are the independent opinions of the Vine Voices. The vendor cannot influence, modify or edit the reviews. Amazon does not modify or edit Vine reviews, as long as they comply with our posting guidelines. A Vine review is identified with the green stripe Customer review from the Amazon Vine Program."
They classify the reviews as positive or critical, so far there are 15 positive and 1 critical, here's the critical one: