Many of us use and prefer Firefox. It is (at least in my experience) faster than IE in loading pages, it certainly is safer (since it is not part of the operating system unlike IE), and has many more useful features than IE. Moreover, the open source folks at Mozilla make frequent enhancements, and they are much, much quicker to issue a patch for known vulnerabilities than is MS (I hae seen some turned around in less than four days when they are critical).
Firefox itself is well-coded and rather lean; you can, however, install extensions (or plug-ins is another word for them) that can tailor the functionality in the browser to meet your needs,or use it right "out of the box). In a matter of something over a year, Firefox has captured around a 10 percent share (or more) of browser use.
Alas! Because some sites, notably Microsoft Update, will only work using IE (I wonder why that is), and because IE is used by the Operating System, you have to keep it around and keep it patched. You may also need to install JavaRuntimeEnvironment and Flash if they are not installed on your hard drive.
Firefox is free for the download from the good people at Mozilla:Firefox Home Page