Many ISA firewall admins who are currently running ISA Server 2000 or 2004 will want to know why they should upgrade to ISA Server 2006. While the upgrade from ISA Server 2000 to ISA 2004 was an easy one to understand because of the major improvements and changes made between ISA Server 2000 and ISA 2004, the changes included with ISA 2006 versus ISA 2004 are more incremental and provide a much smoother transition than the upgrade from 2000 to 2004.
Most of the new features and capabilities seen in ISA 2006 compared to 2004 are difficult for the average ISA firewall admin to see if only a superficial look at the product is taken. The user interface is the same, the networking model is same, there have been no changes in terms of how the ISA firewall performs outbound access control, and there have been no changes to the core networking and traditional firewall feature set.(continue at source)