Cognos is a robust suite of tools (we use it as a front-end for an Oracle back-end), but there's a pronounced lack of documentation on how to accomplish complex reporting tasks -- mostly, you end up banging on it until you get something to work.
I wouldn't discount the usefulness of using Microsoft Access as a reporting front-end. It doesn't have that useful Web-enabled functionality, but for in-house reports it's very versatile and surprisingly powerful.
