Apple has strangely released a revision to its original iOS 5.0.1 update which was first released back in November. The release coincides with the update to the second generation Apple TV and maybe has something to do with the release of iTunes Match in more countries or the iPhone 4S continued international rollout.
If you have already updated to iOS 5.0.1 you will not see the update; it appears to be only accessible to those that haven’t updated originally. The new build is iOS 5.0.1 (9A406) and supposedly offers some small bug fixes and stability improvements.
If anyone updates to the new version let us know if you notice any changes.
Source: TiPb Forum