to support the use of Maxima vs other CAS eg. Maple, Mathematica ... and let the ones who argue Maxima, or its technology (eg. usage of lisp) is not a good idea in 2007
The most important argument for me is that maxima is free/open-source software. Therefore I can ask students to use it for coursework without asking them to use non-free software or worry about licenses. A related reason to use maxima, applicable if you are a US taxpayer, is that you've already contributed to its development through government funding.