To answer my own question: I found that both Classilla and iCab did a better job with modern web pages, but both are mind-numbingly slow on this machine. iCab did a nicer job of rendering graphics into 256 colors, and seemed a little faster perhaps. Classilla did a better job with the Comcast web-mail page, although neither browser was able to handle the page well enough for me to actually send email.

As I type this now (using iCab), I am easily able to type ahead 10 seconds and 30 letters ahead of what's echoed back to the form in the web page. I guess a 120 MHz 604 just isn't up to the task.