Curtis Herbert, creator of the excellent Slopes for iOS (I wish I was a skier or snowboarder to use his app), has some great tips for developers on dealing with replies to App Store reviews:

I’d recommend every app owner do the following, today. Head into the review section in iTunes Connect and sort by “Most Helpful.” These are reviews that customers have voted should be floated to the top, and that’s what Apple does. Take a quick look through there and see which ones you can address.

Future customers are most likely to see your replies to these reviews, so that’s the best bang-for-the-buck you can do right now. I went further than that, personally, and re-read a ton of my negative reviews and replied to the ones that met the above goals, but you don’t have to rush it.

If you’re a developer, you’ll want to start engaging with customers right away and work through your existing backlog of reviews. I have a feeling the new ability for developers to reply to customers will fundamentally change the tone and utility of App Store reviews.