...like Firefox, but for OS 9?
No, no. More like Netscape Navigator to Classilla's Netscape Communicator. But yes, for OS 8.6 and 9.
it does very well at doing things that the rest of the world feels needs a 3GHz+ Multi Core cpu to do.
Well, you see, I have this strong suspicion that the sort of people who make Web 2.0 sites and use AJAX and do things that need eleventy million megahertz to render properly tend to be the same sort of people whose sites suffer for want of stimulating content, so it's generally no skin off my back if any of my Power Macintoshes is incapable of rendering facebook