The single biggest weakness (or gap) in our ability to provide amazing customer service is that a lot of people still use iTunes App Store reviews to communicate their issues but there is no way for us devs to contact those people to help them resolve it. Apple needs to fix this one-way channel.
This is very frustrating. I don't think users realize there is no way for developers to get back to them and so many questions go unanswered. In the end I wrote a script to pull all the reviews into my apps site so I can post comments there and I let the users know that in the app. Plus now it's also easy for me to send myself a notification for a new/updated review. Seams to be working so far as some users have come back and added comments.