A quick fedora/nvidia tip:
After installing the evil and freedom hating nvidia-drivers on my Fedora system, a lot of font sizes magically increased. It seems you can fix this (per user) by clicking ‘System’, ‘Preferences’, ‘Appearance’. Click the ‘fonts’ tab, then the ‘details’ button, and change the resolution back to 96 dpi.
You can probably change this in some configuration file as well. If you know how, please let me know.