Cognos questions

Hi Folks, Some of you must be using Cognos reposrt writer. I would like to know how this works. Does it create views/superviews on the database? does it create temp tables on the DB ? Or rather does it write anything to the Informix database. I am evaluating this product and would like to know about these from you all. Let me know what you feel about the product its advantages and disadvantages. Thanks in advance, Sudhir Nair