Depending on the version of IE you use, it can be a standards breaker (i.e. pages that work on IE do not work well on other browsers or vice-versa). It may also be slower than other browsers (as I remember IE 7.0 vs Firefox 1.5 anyway), has support for ActiveX (security vulnerability) and has no support for extensions that customizes its behaviour. For at least me, I really did not like the idea of using a browser that broke the HTML/CSS standards. But if you're just looking for a web browser that only browses the Internet regardless of its problems, well... Internet Explorer does work.