It has a particularly nice user interface, with a smoothness that only Amiga hardware can give. So it is useful for decision support, to help you clarify complex ideas. Version 1.1 has Knowledge Server capability. That is, knowledge bases created by Istar can be run over the Internet, worldwide. You build your knowledge base by drawing boxes and arrows, and then can run the KB either direct or via a browser.
Most documentation is now in html.
A number of other changes have been made, bugs fixed, etc. to the main Istar since version 1.092. But the major change is that Version 1.1 has been made into a knowledge server. That is, Istar can converse with a distant browser. Though the modular nature of Istar made it easy to get an initial version working, the inference engine required an overhaul before it could support multi-user access. Help buttons are now available on forms.