I used to use this in college before I switched to Camino!
Camino was snappy, clean, and had very good standards compliance. Such a great little browser!
I actually paid for it. Sad that there's not much to choose from nowadays.
I even had a short look on how hard it would be to use the shell for a more modern engine, but it seems deeply entrenched in the Mozilla codebase, which is basically a dungeon full of undead, dragons and rust monsters.
I still have it on my Mac, but it's only good for checking how pages look like if they're viewed on a browser that doesn't support the latest web standards.
IE on Mac had its very own class of display errors and incompatibilities, making webdevs' lives even more miserable than they were before.