Here is a short note on how to (at least) partially fix ghastly default fonts that SQL Developer is cursed with it on Linux. After I installed the recently released SQL Developer 4.0 on my Fedora 19 workstation, I immediately increased the font size from 11 points to 14 by editing:

$ nano ~/.sqldeveloper/system4.0.0.13.80/o.sqldeveloper.12.2.0.13.80/ide.properties

# To modify the font size for all look-and-feels in all locales, set
# the Ide.FontSize property.  For example:
Ide.FontSize=14

…plus, I changed the way how Java is smoothing fonts by adding two variables in product.conf file:

$ nano ~/.sqldeveloper/4.0.0/product.conf

AddVMOption -Dswing.aatext=true
AddVMOption -Dawt.useSystemAAFontSettings=lcd

Make sure that SQL Developer is not running while editing product.conf file, because it’ll overwrite your changes at exit!

And here is, somehow prettier SQL Developer IDE: