From a source on the internet IOS 5.1 is to present some notes and issues addressed include the Apple Account ID, GameKit, iCloud Storage, Movie Player, Newsstand, Security, Xcode / Developer Tools.
His name alone IOS 5.1 for developers, of course, this update is more geared for developers who like to "tamper" daleman Apple. It could be from the developers will be present application development better.
IOS 5.1 is can be tried in devices like the iPhone, iPad, and iPod. And if you're a developer and have the data on the Developer Center you can get the latest update of this IOS, and certainly more able to understand the presence of IOS 5.1 is.