As that is my main browser; I have plenty of plugins, eg: noscript, ghostery. However I also use opera for those sites where it is too much of a pain to work out what scripts/references to allow, etc -- and then get it to forget everything once I have viewed the site. The combination works well at maintaining privacy.
Firefox has good plugins that help with web development, but Opera's Dragonfly is very much worth using as a complimentary tool. I also use Lynx to check pages, partly because it shows me how spiders see the site -- good for SEO.