I was reading the Exchange team blog, You Had Me at Ehlo…, today and read their post regarding permissions for SP2.
SP1 for Exchange Server 2003 can be installed by an Exchange administrator for the administrative group where the Exchange server lives and a local administrator on the Exchange server. Things have changed, though, for SP2.
Now, for SP2, the initial installation must be done by an Exchange Administrator at the organization level. The reason it has to be done at the organization level is because the Intelligent Message Filter (IMF) is part of SP2 and it requires and Org level Admin to install it properly. After the first install is done, then Exchange Admins can perform the installations in their administrative groups.
Note 1: If IMF versions before 2.0 are installed, SP2 will require that they be removed before installing SP2.
Note 2: IMF will be installed on cluster nodes but will be disabled and will not function on cluster nodes as it is not supported in Exchange clustering.