I added code to lookup in the registry based on the fontName. This is only applied to windows though, so it means if you use a FontName in your spritefont on a Mac the chances are it wont work, unless the Font Filename matches the FontName+.ttf etc. However the improvement is if you use the Font filename, you can just drop the font in the same directory as the .spritefont file and it will pick it up without having to install it.