iOS 5.0.1 was released by Apple in two versions, build 9A405 and 9A406. The second build was released to help correct a problem affecting iPhone 4S owners receiving a "No SIM Card Installed" error on their devices. The update was not released as iOS 5.0.2 to all users since the fix was specific to the iPhone 4S and was only intended to help a small number of users affected by the problem.
Apple has planted fake device listings like "iPad10,1" and "AppleTV8,3" in configuration files to throw off developers looking for future iOS devices in their new iOS 5.1 beta 2. Mark Gurman (via MacRumors) discovered that the devices listed in the file, USBDeviceConfiguration.plist, went from around two dozen to over 100 items since the last release.
Besides the amusing fake files, iOS 5.1 beta 2 hasn't revealed anything too interesting. There are a few new bug fixes and the ability to remove images from the iCloud Photo Stream. The previous iOS 5.1 beta featured a possible battery drain fix, and an inactive code in the Camera app that allows panoramic photos.
The first beta of iOS 5.1 has been seeded to Apple developers, and includes several changes and improvements. First off, code has been uncovered pointing to support for a new piece of hardware, namely a Sprint iPad 2. Apple launched the iPhone 4S and iPhone 4 on Sprint's network just recently, and it appears they are taking the next step.
Other changes spotted by 9to5Mac include a new setting in Location Services for geofencing. One source of battery drain is geofencing, when an app such as Reminders puts a virtual perimeter around a location. Notifications are sent when leaving or arriving the location, and in iOS 5.1 each app that uses the feature has a special icon in Location Services.
Apple has added OTA (over the air) updating capability to iOS 5. This means that instead of having to download hundreds of MB of iOS software to your computer you can easily update directly on your device. No more connecting the iPhone to the computer and waiting for the entire operating system to be replaced in its entirety. Only the portions of the firmware that need to be replaced are downloaded.