As reported by TechCrunch, Apple appears to have tweaked the search algorithm of the App Store over the past few weeks, leading to more consistent results:
According to multiple sources, including developers who tracked their own rankings, as well as app store analytics firms, the change that began November 3 included several adjustments. Apps are now ranking in search results on a mix of contextual keywords for the app, including partial keyword matches, along with competitor brand names and other matches.
I'm curious to see how this latest change will affect independent developers over the next couple of months. For better or worse, search – not the Store's curated Explore section – is still the easiest way to find any kind of app. A major change to the search algorithm can potentially affect the livelihood of thousands of indie developers.