So, being the anal type, I just checked and, out of 103 reviews, I've gotten 17 author replies. Out of 17 replies, I've responded to eight -- three with replies to the replies and five with e-mails. Three of these replies have resulted in ratings increases.

I think most of S_Coutures plaints regarding how hard it is to reply to a review also apply to responding to replies. When an author says "Thank you for reviewing", what is left to be said? The replies I've responded to have MOSTLY been those in which authors gently disagree with me, sometimes providing me with additional information (though it could be argued that information not in evidence in the story has no business influencing the review, I tend to be lenient in this regard).