I eat it once a month maybe. Gotta love the McGangbang though... surprisingly good. Also, if you want a cheap Big Mac, just get a McDouble and ask for Big Mac sauce... they'll charge maybe 30 cents for it, sometimes free. Can't go wrong with that.
And to the guys saying its the main reason Americans are fat- that's completely false. Laziness is the main reason. No one forces anyone to eat McDs or not exercise. McDs is fine, as long as it fits into your caloric needs for the day