Well, I have several installed. Internet Explorer, Firefox, Chrome, and Opera (most of which I'll be uninstalling soon). The only one I regularly use is Firefox, as it's customizable enough to suit my needs.
Internet Explorer is mediocre, but maybe I'm just inexperienced with recent versions. Chrome is pretty good, but it's still a bit more restricted and it doesn't have a fully-functional Noscript addon. Opera is also pretty good, but I haven't had a reason to use it enough to really explore it.