"If you use Gmail on their website -- as I do --" says Jim Hamm, "soon there will be a change to the 'Compose' format: it will go full-screen. Take a read here. This will be a welcome change.
"If you download Gmail emails into your computer's email program, you probably won't notice any change as the formatting will be specific to that particular program, such as Mail, or Thunderbird, or whatever."