The feature that I have found the most useful is the decode of packets. It gives us a variety of information that helps us in figuring out what to look at. The networks are getting really complex, and without the information that we get from Iris Session Analyzer, we couldn't do our job.
Its graphical user interface is also very easy to use and intuitive.
They can increase flexibility in the search engine. Basically, I go with the information I have at the time. If I could just type in the parameter that I want to search for and its value, it might be easier than having to do the groundwork upfront before I can get my traces.