De following list calls out the most important fixes which are included in this release:
22653334 The reseed process is unsuccessful on the SCR passive node when the circular logging feature is enabled in an Exchange Server 2007 environment
For the complete list check HERE
Note for Forefront Protection for Exchange users For those of you running Forefront Protection for Exchange, be sure you perform these important steps from the command line in the Forefront directory before and after this rollup's installation process. Without these steps, Exchange services for Information Store and Transport will not start after you apply this update. Before installing the update, disable ForeFront by using this command: fscutility /disable. After installing the update, re-enable ForeFront by running fscutility /enable.