The first chapter of Internet Programming with Python also examines some of the reasons for using Python. The book is well worth buying, but the publishers have made the first chapter available on the Web.
John Ousterhout's white paper on scripting is a good argument for the utility of scripting languages, though naturally enough, he emphasizes Tcl, the language he developed. Most of the arguments would apply to any scripting language.
The authors, David M. Beazley and Peter S. Lomdahl, describe their use of Python at Los Alamos National Laboratory. It's another good example of how Python can help get real work done. This quotation from the paper has been echoed by many people:
Originally developed as a large monolithic application for massively parallel processing systems, we have used Python to transform our application into a flexible, highly modular, and extremely powerful system for performing simulation, data analysis, and visualization. In addition, we describe how Python has solved a number of important problems related to the development, debugging, deployment, and maintenance of scientific software.
This interview with Andy Feit, discussing Infoseek's use of Python, can be used to show that choosing Python didn't introduce any difficulties into a company's development process, and provided some substantial benefits.
Robin Friedrich wrote this document on how to support Python's use in commercial projects.
For the 6th Python conference, Greg Stein presented a paper that traced Python's adoption and usage at a startup called eShop, and later at Microsoft.
Management may be doubtful of the reliability and usefulness of software that wasn't written commercially. This site presents arguments that show how open source software can have considerable advantages over closed-source software.
The Linux Advocacy mini-HOWTO was the inspiration for this document, and is also well worth reading for general suggestions on winning acceptance for a new technology, such as Linux or Python. In general, you won't make much progress by simply attacking existing systems and complaining about their inadequacies; this often ends up looking like unfocused whining. It's much better to point out some of the many areas where Python is an improvement over other systems.