Forefront UAG 2010 SP3 update is a pretty strait process. In my case my UAG Box was dedicated to DirectAccess. If the update process is strait forward, there is one thing to do not forget after update : reconfiguring DNS64 service. By default, this service is reconfigured from Automatic startup type to manual witch cause corporate DNS name resolution to fail for DirectAccess Clients. You can check with a simple Get-Service DNSAlgSvc PowerShell command :
Just reconfigure the Service StartupType property of the service with a Set-Service and start the service.
Enjoy Windows 8 clients connecting to your DirectAccess infrastructure.
BenoîtS – Simple and Secure by Design but Business compliant