Microsoft Exchange service pack two is now available for download.
I believe that it must be installed on the Exchange server that resides in the same site as the schema master prior to installing it on servers at remote sites..
Exchange 2k7 SP1 fixes a few problems such as not being able to view public folders from within OWA.
It also adds some functionality to the GUI that was only available through the CLI on the RTM version.
Download links can be found below.