I recently posted about the availability of Exchange 2010 SP1 and thought I would provide some feedback about the installation process.

Before installing SP1 for Exchange 2010, there are several updates and hot fixes that need to be installed first. An important thing to note is that all the Unified Messaging language packs other than US English (en-US) need to be uninstalled before upgrading the Unified Messaging server role. I have split these up then up by server role:

Hub Transport Role Prerequisites:
Microsoft Knowledge Base article 979099
Microsoft Office 2010 Filter Packs

Client Access Role Prerequisites:
Microsoft Knowledge Base article 982867 *requires a restart
Microsoft Knowledge Base article 979744 *requires a restart
Microsoft Knowledge Base article 983440 *requires a restart
Microsoft Knowledge Base article 977020
Knowledge Base article 979099

Mailbox Role Prerequisites:
Microsoft Knowledge Base article 979099
Microsoft Office 2010 Filter Packs

Unified Messaging Role Prerequisites:
Microsoft Unified Communications Managed API, Core Runtime 64-bit
Microsoft Server Speech Platform Runtime 64-bit
Microsoft Knowledge Base article 979099