Like I said, not for the beginner. Then again, what else am I supposed to use? Mac has by far the best hardware and OSX is a giant piece of crap for power users.
I would try mint linux, but I'm too afraid of being stuck without support.
I've thought of making a small side company that only sells rMBPs with dual boot ubuntu at a 200 dollar markup. I'd pay that, but maybe I'm not your normal computer user.
Whenever I encounter a site that doesn't render properly with large fonts, I simply turn off the minimum font size in Firefox and use the OS X Accessibility keyboard shortcuts to zoom in. This works well, but it's annoying to have to keep switching around like that. E.g. it would be nice to have faster access to the Firefox submenu that controls minimum font size.
I find if I'm tired, I need to increase the zoom to read text, so a quick mouse wheel while holding Ctrl and then a Ctrl-0 when finished and it's like it never happened