Following Google IO 2012, Google announced its new feature for app publishers, which is a great thing; replying to user reviews on Google Play.
Sadly, they enabled it only for top developers. And they added they will offer it to additional developers based on feedback from users and developers.
This feature will help developers to respond to user reviews which mention a fixed bug or something not valid anymore. Even though the reviewer does not delete his review upon the reply, people seeing the review and reply will understand that the problem is no longer valid. This feature will be very useful for that purpose.
To be honest, I'm impatiently waiting for this feature to be active for all developers. Come on Google, make it open for everyone. We know that you can do it.
Android Developers Blog: Replying to User Reviews on Google Play