People on here have surfed on 1-bit displays. My step-dad used to dial in to Motorola in the mid-90s on a Classic. I think I used it to hit a few sites, as well, though I only remember that it was excruciatingly slow.
As for me, I've used my 520 (7.6.1 w/36MB RAM) to get online. It wasn't as bad as you might think. It was actually relatively usable, and didn't look too horrible. Then again, I only loaded this page, Yahoo!, and Apple's main page. Homestarrunner.com would explode that thing (if it could comprehend Flash, that is), as would any graphics-intensive page.