If you haven't tried it, it's worth giving it a try IMO. It's very stable, certainly better than Netscape 4.7x or 6.x. The only minor drawback is that the free version has a small ad in the top right corner, but it's no big deal.
I've found it loads pages significantly faster than IE with default settings. (You
can tweak IE to make it nearly as fast though... ) Most every page looks correct, although there are some that look a little funny with text positioning. (AH homepage is one of the few I've found.)
What's interesting about Opera is the fact that you can have multiple browser windows open at the same time AND on the screen at the same time. It is also certainly more secure than IE.
Some other nice things:
You can turn off pop-up ads!
Extensive customization options.
It runs using the Sun Java VM, meaning there are versions for nearly every type of computer.
Very nice websearch function.
Right click shortcuts. (For example: clicking the right mouse button and doing a quick stroke to the left is like clicking the back button.)
http://www.opera.com
