While Apple has previously released most of the betas on Tuesday, a desire to prevent the "pink screen of death" associate with expired betas perhaps necessitated an earlier release this time.
The OS weighs is said to weigh in at around 307MB. Updates to follow below as we get them:
According to WhenWillApple, you can now copy and paste videos into email (like you could images under 3.0) to get full resolution (not compressed like the share option). We're guessing email box size will still be a restriction...
Also, Tethering Data now gets it's own counter in Settings > General > Usage.
[Thanks to Davizzle for the tip!]