Never had a problem.
I will advise that you pick a laptop bag which is easy to get the MacBook in and out of quickly. In the U.S. at least (and as you may well know), all laptops have to be out of the bag and in their own plastic bin as they go through screening. So a bag that allows you to get the MacBook out, and then returned to safety with minimal fuss is a blessing.
You don't want to be fighting to get the laptop in and out of a bag while also trying to maneuver shoes, wallet, cellphone, etc.