Looks like the good folks over on the MDOP blog just announced the immediate availability of Microsoft App-V 4.5 SP2:

App-V 4.5 Service Pack 2  provides the latest updates to Microsoft Application Virtualization 4.5 code line. This is the first time the team has delivered via Windows Update App-V 4.5 SP2 introduces:

• Enhanced failover protection or disaster recovery of your virtual application infrastructure: App-V data-store failover protection enables administrators to quickly recover from disasters and/or recycle servers for maintenance.
• Enable highly available application infrastructure: App-V 4.5 SP2 load balanced management servers can now leverage SQL server mirrored data-store to support high availability scenarios for line of business applications; with automatic failover protection not available with the previous versions of App-V. 
• Data replication is now possible across geography: this enables organizations to recover from site wide failures faster.
• App-V 4.5 SP2 clients can now deploy Office 2010.

To learn more you can get all the details straight from the source.

J.C. Hornbeck | System Center Knowledge Engineer