I hadn't noticed any problems specific to the forums here, but the display changes made in Firefox 22 (final release, too) definitely messed things up for me when viewing web pages generally. I've got a 19" flatscreen which I normally keep set at 1024x768 as a reasonable compromise between page content and comfortable viewing. After upgrading to 22, suddenly every page was too wide for the screen and required scrolling. No problems with blurry fonts, though.
Thanks, Tetsuo, for that link to the specific topic at the Mozilla forums. A single change suggested there worked beautifully in getting things back to normal for me ... in about:config, changed the value of layout.css.devPixelsPerPx (should be the first entry in that section) from -1 to 1. Didn't even require restarting Firefox.