This isn't the larger iOS 5.1 update that's currently in the hands of developers, but Apple has seemingly re-released 5.0.1 today with a new build — 9A406 instead of the earlier 9A405 — that's only available for the iPhone 4S, specifically. Well-known iOS hacker MuscleNerd recently tweeted an unusual observation about the update: it's the first official 4S firmware with an accessible encryption key for the main file system, meaning you can browse the file system from a PC unimpeded. Lots of folks are pointing out that this means users will be able to get at Siri's files without committing piracy, and that could lead to a field day for Siri hacks. There's no official word from Apple at this point on exactly what's changed.
Apple releases new build of iOS 5.0.1 for iPhone 4S
Apple has released a small update to iOS 5.0.1 today, available on the iPhone 4S.