i work with the internet, doing research and making websites for money.
IE doesn't conform to the internet standards laid down by the W3C, and websites can appear to be broken in them. problem is for a long time it has been the dominant web browser used by web users. but that is soon to change!
Firefox is a browser than conforms to web standards, it's fast, secure and can be easily modified. It's a great browser, and everyone should at least try it.
Opera on the other hand, is at the top of the table, along with safari, knoquer (Sp?) and Shiira (all which can't be used on windows bar opera) is at the top if it's league, it conforms to everything that the W3C emply, and it can't get any better..
Now you have to remember, each browser acts differently on each different system, IE might work better on one persons computer compared to firefox, whilst on a different computer, firefox will be the best.
For me i use every browser, netscape, shiira, konquere, safari, seamonkey, firefox, lynx.command, camino, omniweb, IE and a few others. i use camino on a daily bassis tho.