Because you can effortlessly do things in Firefox that IE users only dream about, without giving up most of the compatibility in the IE world that you need.
Some of the favourite features of firefox that you would definitely miss in IE are :
- Tabbed Browsing - Makes surfing the web faster
- Popup Blocking
- More Space for Pages
- Personalize With Themes
- Customizable and Extendable with extensions
Upgrading from IE to Firefox is only a bit more difficult than, well playing solitaire. Basically all you need to do is import your favories from Internet Explorer. And the best part is that this is already done while your install Firefox.
Replace IE and disable it !!