The latest Update from Microsoft has been release for Exchange 2010 SP1. This updates contains lots of fixes and improvements that should be noted. The update fixes a few crashing services bugs and addresses a few performance improvements.
The list of fixes can be found at http://support.microsoft.com/kb/2509910
Original post on the Exchange Team Blog http://blogs.technet.com/b/exchange/archive/2011/06/22/released-update-rollup-4-for-exchange-2010-sp1.aspxTweet