At MozCamp Warsaw, a presentation was given on the design principles behind the core Firefox OS experience. Layering of applications (if you're wondering why the Firefox mobile interface has that weird curve by the tab control, you'll find answers here), an emphasis on content over visual frills for their own sake, consistent iconography, and clean typography dominate.
Utility is when you have one telephone, luxury is when you have two,
opulence is when you have three -- and paradise is when you have none.
-- Doug Larson