Apple’s new iOS 6 App Store application has received a major overhaul, bringing its Genius button to the forefront of the app and with changes to the algorithms that govern ranking.

The news, which got lost somewhat in the flurry of new devices launched last night, will nevertheless prove crucial to developers as they look to bring their iOS apps to the attention of the largest audience possible.

Consumers will see the changes when iOS 6 launches on September 19, although news of the changes had already leaked among the developer community.

Changes to the look and overall feel of the app include Genius replacing the “Categories” search on the app’s main screen, according to TechCrunch, with Apple effectively encouraging consumers to search for apps based on its recommendations over the age-old principle of category. It has also introduced “card-like” mechanism for browsing through apps.

Under the hood, however, is where the real interest lies for developers and changes suggest that Apple’s acquisition of Chomp may well prove pivotal. Back in June we reported that the App Store’s search algorithm appeared to have been tweaked, valuing downloads and ratings over pure keyword-matching, in a move that was in line with Chomp’s promise to search “based on what apps do, not just what they’re called”.

According to app analytics firm SearchMan, the App Store has now changed its algorithms again and this is already affecting the ranking of well-known brands such as Amazon and eBay (up) and Home Shopping Network and Stop and Shop (down).

What the exact effect on rankings will be probably won’t become clear until months after iOS launches. But with more than 700,000 apps currently in the App Store, according to Apple CEO Tim Cook, these changes are likely to prove crucial.