I’ve updated my iPhone 5 already, but never had the issue in the 1st place on my server so can’t confirm it is resolved. Here’s the text of the update message:

Fixes and Exchange calendar bug that could results in increased network activity and reduced battery life.

http://support.apple.com/kb/DL1639

See Tony Redmond’s post for more details: http://thoughtsofanidlemind.wordpress.com/2013/02/19/ios6-1-2-appears/

For more info on the issue my post here: https://blog.jasonsherry.net/2013/02/10/ios-6-1-causing-very-high-log-generation-on-exchange/