The firmware is currently available via Software Update and through the dev center shortly. The delta update is 263MB for the iPhone 5 and 207MB for older devices
The last update brought many fixes and changes which we logged here.
We'll update you with any change we find, but if you see anything, please let us know in the comments below!
Also, we will let you know if the update is safe for those without a registered developer account using the update trick soon.