I have always used IE. Even when Netscape was around. However, about a month ago I was introduced to Chrome. It was fast, sleek and exciting. Then I found the limitations. So with no print preview as the final straw, I uninstalled and put in Firefox. I like its speed and cool features (like bookmark folders and open all tabs, which I'm sure IE does as we'll).
With that said, I still have to use IE for some things, especially when something doesn't load like it should in Firefox (which happens about 20% of the time).
If Microsoft speeds up the browser to rival the load speed of the competitors, I'd keep IE and drop the rest! Initial load times on a fresh OS install with no addons shouldn't take more than 5 seconds!
So for now, when I add new people to my business team, which I'm always looking for, I tell them to use Firefox. When your focus is building a very profitable business, speed is of the essence!!!