I used this for a flight to Spain and it 's ability to block out the drone of the airplane's engines makes flying all the more bearable.
They fold flat into a nice case which would fit in to your hand luggage without a problem.
I would say they are worth it over the more expensive active noise cancelling headphones available and they use standard AAA batteries. Yes, putting the batteries in is a pita but if you don't have gorilla hands you should have no problem.
People go on about they might not feel sturdy and strong but they are headphones, not head armour. If you want headphones that can last a long long time buy the Sennheiser HD25-1-II BE... I have had my pair for 12 years and though they are not active noise cancelling, they do a fair attempt at blocking external noise.