Today Microsoft released a white paper by Greg Taylor (Sr. Program Manager, Exchange Server Customer Experience Team) on publishing Exchange Server 2010 with Forefront Unified Access Gateway 2010 and Forefront Threat Management Gateway 2010. This white paper contains information and guidance on publishing Exchange Server 2010 using Forefront UAG and Forefront TMG. This includes information on how to choose between UAG and TMG for different scenarios as well as steps on how to configure thos products in order to publish Exchange 2010.
You can download the white paper here.