Although the Bose are slightly more comfortable and play back music better, my $50 Targus headphones are actually superior when it comes to noise cancellation (determinted by side by side comparison). They offer 16db max cancellation, which is 6db above the posted specs of the other NC headphones I looked at (Sony, etc) - and Bose doesn't even publish theirs, which I would understand if their headphone tolerances are as poor as their speaker specs.
Are the Bose nice headsets? Sure. Are they the best headsets for noise cancellation? No. Are they worth an additional $250? You'd have to be a fool....