I used Opera for about the last year since I was using a p200, the newer versions of IE and netscape just used too much system resources, and my crappy hsp winmodem was crawling. Once I switch to a hardware modem I didn't notice to large a difference between IE and opera. Netscape was still slower and more crash prone. Not to bash Netscape, I started using it in college and still like several features it has. I resisted IE for years (3 just blew, 4 was ok, 5 is good). Now I have winME and IE 5.5 is built in, I don't think I can remove it if I wanted to.
back to opera...
Are you using the new version of Opera? I had 3.xx and it was great for someone on a slow connection. The ability to turn off images in one window and while viewing images on other pages saved me hours of downloading eyecandy junk. The lack of plugin and mail support was annoying, and forced me to keep a second browser on my system. The small download size gives Opera a big advantage in terms of ease of install.