Microsoft have released ISA Server 2004 Service Pack 3, which includes support for Exchange Server 2007 and updated log viewer functionality:

Internet Security and Acceleration (ISA) Server 2004 SP3 provides the latest updates to ISA Server 2004 Enterprise Edition, with increased security, new troubleshooting tools, and improved log viewer functionality. This service pack also adds support for publishing Microsoft Exchange Server 2007 with ISA Server 2004. We strongly recommend customers install ISA Server 2004 SP3 on all computers running ISA Server 2004.

There’s also a new diagnostic log viewer which looks interesting, I’ll have to check it out. Hopefully this means that ISA Server 2006 will get the same functionality updates as well.