I work with a big jet modified as a research aeroplane - normally flying with a crew of 16-20 (2 pilots, 1 CCM, others mostly scientists). Recently we did an in-flight assessment of alternative headsets - covering the DC H10-34, Bose-X, Lightspeed 20XLC, Lightspeed Zulu, Senheisser 460 and an old Telex passive.
By a large margin the Bose-X came out top after a parallel assessment over 8 5ish hour flights, followed by the DC. The other ANRs all had problems which made them unacceptable for the task (although I'm sure they're fine in other aeroplanes), and the Telex were poor but just about okay.
So we bought Bose-X for everybody except the two pilots (who have stuck with a preference for DC) and they've worked extremely well in about 75 hours of operating flying since. The 27 Bose-X headsets we bought probably made for a good Christmas bonus for the salesman, but they were worth it. (Yes we did get some discount, but only about £50/headset).
G