Dave, Why is it that, “out of the box”, the Firefox browser looks great (font wise) when run on a Windows OS but looks terrible (almost too small and unreadable) on any Linux OS I have tried it on. It is probably the number one killer reason for me not switching to Linux.
At a standard screen resolution of 72 dots per inch, any small typeface is going to look pretty mediocre, and I know what you mean about Linux defaulting to a really high resolution for a given screen, which produces tiny type.
However, it turns out that it’s pretty easy to change your desktop to have larger typefaces, or even to tweak Firefox to look better. The easiest way to have larger type across your entire Linux experience is to simply pick a smaller screen resolution. If you’re at 1280×1024, for example, change it to 1024×768 and watch how everything gets a bit bigger and easier to read. Depending on your desktop and window manager, you might also be able to pick a different theme that has larger fonts too.
Within Firefox itself, you can change Firefox font settings from the Edit -> Preferences menu item (pick General, and click on “Fonts & Colors”). Pick a larger font, reload the page, and see how it looks. Of ocurse, you can also just use the key combination Ctrl-+ (the Control key and the + symbol at the same time) to make all the type on a Web page larger. I use that extensively when I browse the Web too, actually.
Hopefully those tips will help you out and let you give Linux another shot. I did ask a couple of Linux wizards, Dee-Ann LeBlanc and Ray Lischner, about this problem and they reported excellent results with Firefox on Suse Linux, Fedora and RHEL.