I really don't understand everyone immediately responding with a "unbutton the top button." I know that it isn't in fashion right now, but it harkens back to 1960's England...which provided the look isn't outlandish...gives any fit credibility.
There are some jackets that I have a 3 roll 2...the lapel rolls enough naturally that I've had it lightly pressed into a 3r2. Other jackets have flat lapels and so I fasten the top button. I like the way it looks and it just looks sloppy otherwise.
I would really like to hear the aesthetic analysis behind avoiding that top button. It doesn't work for all body types, but I'm 6 feet with shoes and have the right torso shape.
It looks uptight to me. There's no ease to it. You can't unbutton it to sit down easily, either.