I recently switched from IE to this Browser, I have no regrets.
Firefox has a very clean interface, built in popup blocker, support for download resume.
You can install Firefox parallel to Mozilla, it'll use its own profile and won't interfere with your Mozilla profile.
Mozilla 1.6 is currently a browser suite including the browser, email, HTML editor and a basic chatclient. The Mozilla developers are trying to split this suite into a lightweight browser (Firefox) and mail program (Thunderbird).
Hehe, there're even some former die hard IE users who recently switched to Mozilla / Firefox (I've been using Mozilla for over 4 years).