Mine are Sony and they help on long flights. Had 'em about 7 years or so but where only available in the UK for 2 years - but saw them on sale in Kuala Lumpa airport in 2000. They are ideal for reducing the noise - you do still get the high frequency through which sounds louder and as an electronic engineer I am pretty certain it is not all subjective. The audio is definitely louder when you switch the cancelling on (by a small amount) and that IS techno-marketing. I find two minor problems 1) if you cover the microphones (or the air holes it not only ruins the effect but is noisier, and 2) depending on what they are plugged into (just about everything) I pick-up 50Hz (60Hz?) inside most buildings and whilst driving under some power cables. BUT the plus is it makes the redmobile almost acceptable in the axle noise dept.
Most of which is arbitrary if you just want them for flight. So keep in mind you can't really sleep on them but if you find a comfortable position otherwise you definitely can sleep in them. Mine came with a funny little twin-pronged converter (one leg folds and it then doubles as a stereo to mono converter)- keep that safe because there are still airplanes with twin-pronged sockets though my last flight (737 I think) was a single prong outlet. They are physically about the size of your ear and not cupped over the ears - those Sennheiser models would be better for noise cancellation but not for the sleeping.
Oh and if you hear a banging plop once a minute - it is the (single) battery needing changing. I love them.