There is an interesting article on using user stories for non-functional requirements in agile software development projects in the last issue of Methods & Tools:
http://www.methodsandtools.com/archive/archive.php?id=113

I'm am the Lead BA in my organization, and am struggling with a particular issue regarding requirements documentation.  I work for an insurance company and typically the projects in the portfolio have some IT componenets, usually changing parts of the Legacy systems to accomodate new benefits, but our BA's also work with the business units to understand the things that need to be done to complete the project that are not IT related.

The BA's document the IT requirements and the non-IT requirements in our Project Requirements Document (PRD).  The BA's typically document these non-IT requirements as "Business Requirements".  I disagree with the categorization of these, as I think of Business Requirements as much higher level, but there really isn't any other place in our document for these.  Some examples of these requirements are:

There has been much debate as to what "concurrent users" mean in the non-functional requirements area.

Is it the number of people who are concurrently on the same transactions?

Is it the number of people who are currently logged into the system?