I've found that the default font used by textfmt leaves a little to be desired during the rendering process. I realize that this is more a ghostscript issue than a FlexFAX one, but I was wondering what other users of FlexFAX have found. [...] I tried using Type 1 fonts, rather than the bitmap ones supplied with ghostscript, and they don't look any better.
If your observation is based on a preview using Ghostscript 2.6 or later, try running gs with -dNOPLATFONTS (alternatively, you can add "Ghostscript*UseExternalFonts: false" to your X resources if you're previewing with X).