It's that time once again, iOS developers! Apple just posted the beta version of iOS 5.1, which features the build number 9B5117b and is available for download on the iPhone 3GS, iPhone 4, iPhone 4S, iPad, iPad 2, and third and fourth-generation iPod touch. As usual, the iOS 5.1 beta is only available to registered developers and can be found inside Apple's official iOS Dev Center.

The last bit of new software that Apple publicly released was iOS 5.0.1, which was said to contain fixes for bugs affecting battery life among other improvements. Unfortunately, not all users saw their battery life woes disappear, and some folks actually reporting worse battery life after the update. Apple at the time said that it was still looking into "a few remaining issues." There's no mention of more battery life fixes in the changelog for the iOS 5.1 beta, but that doesn't necessarily mean that there aren't any included in the update. As for when iOS 5.1 might be released to us regular folk, well, that's still a mystery at this point, but the good news is that iOS users are one step closer to the next major update (and hopefully the end of their battery woes). The full iOS 5.1 beta changelog is available below.

UPDATE: After diving deep into the code of the iOS 5.1 beta, the folks at 9to5 Mac have found references to a new iPad, dubbed "iPad 2,4." The site suggests that, since the brand new iPads expected to arrive next year will likely be iPad 3,1 and iPad 3,2, this iPad 2,4 model may be the Sprint iPad that we first heard rumblings about back in September. Check out a shot of the iPad 2,4 reference below.

Accounts

• When creating an iCloud account, you can use any Apple ID as long as it is a full email address and not a MobileMe account. If you have a MobileMe account, you can move that account to iCloud. You can find more information at: http://me.com/move

APIs

• The NSNetService class and CFNetService APIs do not include P2P interfaces by default. To browse, register, or resolve services over P2P interfaces, an application needs to use the Bonjour DNSService*() APIs noted below.
• Setting the interfaceIndex parameter to kDNSServiceInterfaceIndexAny in the following API’s will not include P2P interfaces by default. To include P2P interfaces, you must now set the kDNSServiceFlagsIncludeP2P flag when usingkDNSServiceInterfaceIndexAny or set the interfaceIndex to kDNSServiceInterfaceIndexP2P. The affected APIs are:
• DNSServiceBrowse
• DNSServiceRegister
• DNSServiceResolve
• DNSServiceRegisterRecord
• DNSServiceQueryRecord

GameKit

• App Icons and Profile Photos are not loading in apps using Game Center.

iCloud Storage

• Provisioning profiles must be enabled for iCloud in the iOS Provisioning Portal. You can enable a provisioning profile for iCloud by navigating to the App ID section of the iOS Provisioning Portal and configuring your App ID for iCloud. After enabling the App ID for iCloud, regenerate your provisioning profiles to enable them for iCloud.
• The setSortDescriptors: method of NSMetadataQuery is not supported.
• In iOS 5, files that are protected via Data Protection cannot be used with iCloud Storage APIs.
• File names are case-insensitive in Mac OS X but case-sensitive in iOS. This can lead to problems when sharing files between the two using iCloud. You should take steps on iOS to avoid creating files whose names differ only by case.

Movie Player

• Starting in iOS 5.0, in order to facilitate finer-grained playback control, a movie player is not automatically prepared to play upon creation. Call the prepareToPlay method to prepare the movie player. For more information, see MPMoviePlayerController Class Reference

Music Player

• Using shake-to-shuffle causes Music app to freeze and playback to stop.

Newsstand

• FIXED: Deleting an issue that was marked as the currently reading issue could cause a crash

Security

• In iOS 5, the signing of certificates with MD5 signatures is not supported. Please ensure that certificates use signature algorithms based on SHA1 or SHA2.

Xcode/Developer Tools

• A bug in the documentation organizer causes an exception when you type in any field in the content area. To prevent the need to log in to the developer website from Xcode, download documentation sets locally using Xcode’s documentation preference pane and enable the ‘Check for and install updates automatically’ checkbox as a workaround.
• “uninstall-devtools” script mistakenly removes files and packages even if Xcode is still running. Be sure to quit any running copy of Xcode before starting the “uninstall-devtools” script.
• The Network Link Conditioner daemon cannot be launched after installing the Networking Link Conditioner without a reboot. You can manually workaround the issue with a restart or by the following command: sudo launchctl load /system/library/launchdaemons/com.apple.networklinkconditioner.plist.]
• In the iOS 5 development tools, it is possible to extract APIs used by an application and have them checked for use of private APIs. This option is offered when you validate your application for app submission.

Via BGR, 9to5 Mac