An interesting thread. I've had two of the Starbucks metal ones - they call 'em bullet flasks. I thought $28 each was ridiculous until I started using them. They'll keep your stuff not just warm, but HOT for hours. I have used them in an a/c, but only in a 182 unpressurised and low down (and no FMC to rest them on).
I would have thought that whatever problems there might be would be alieviated by opening slowly.
BTW, good coffee on a trip does make all the difference.