What do you need it for? Specific back issues? Some medical reason?

Not being flippant, it's a serious question, I've never carried one of those and have only seen one person carrying one and it seemed, to me, to be rather bulky to carry around, especially if you're on a three-hop long haul like East Coast US to Asia. But probably just as annoying if you're on anything more than a direct flight.

Personally I just use a REI Sit Pad which deflates and stores in a small bag about the size of a soda can. It's great if your only need is to not have a sore ... from sitting in concrete hard airline seats for too long. I take mine anytime I have a flight over about 2 hours.

That said, if you need yours for medical reasons, maybe there's someone else with more experience with those specifically... but if you don't there are easier to carry options out there.