ISA 2004 was a considerable improvement over ISA 2000. It was more secure, feature rich and much easier to configure. I find it funny now that I had trouble getting used to how easy it was to configure 2004 as opposed to 2000.
ISAServer.org posted an article on why you should consider ISA 2006 and why it is better than ISA 2000/2004. Given how quickly it followed the 2004 release, I wouldn’t have thought there was much time to make signifcant improvements. Microsoft proved me wrong. It’s a good read and anyone using or considering ISA should give it a read. It would appear that ISA 2006 provides the most benifit to anyone using it to publish function rich web services thanks to new features such as:
- Web Farm Load Balancing.
- Forms-based authentication support for all Web Publishing Rules.
- Kerberos Constrained Delegation.