All other security, browsing, and standards issues aside between IE and Mozilla based browsers, I find that as a web developer, I simply can’t develop web pages using IE any more. It’s to devoid of decent page information. In Mozilla-based browsers, a page info command yields me dates, time, size, forms, images, cache info, standards info, etc. With browser extensions, I can even see the full resquest/response headers, turn off stylesheets, turn off font tags, highlight tables and block elements, show form contents, and even convert form post’s to get’s.
All of that makes my life as a web developer a whole lot easier than using IE. I would switch for those reasons alone, let alone less security issues, and more standards support.