The document update for M14 is up at http://www.wizards.com/wpn/Events/Rules.aspx?category=all

Not a lot has changed. I've written up a summary at http://blogs.magicjudges.org/telliott/2013/07/11/m14-policy-changes-for-players-and-judges/ and it's a nice quick read.

Good luck with your prereleases!

Toby