Working as a webmaster you understand the fact that a lot of what you're doing, you've done before. Repetition of work is a waste of time, so you might as well use the tools that allow for the least amount of repetition. In addition, being an affiliate webmaster puts you in a position where you want to have control over some aspects of your website that other webmasters might not care about. Specific tools for affiliate webmasters can be handy things.
Here are some links to informative, good webmaster tools sites: