I second that - the Etymotics earphones are excellent - I have used them on BA for many years (and just purchased the more sensitive model for an iPod too).
In my unscientific view it is better to stop the noise reaching the ears (Etymotics approach) rather than add out-of-phase noise on top of the noise (Bose et al approach), isn't it?
And if nothing else, Etymotic earphones are very small (put them in your carryon or in your pants pocket or shirt pocket!), and:
(a) They can be used before airline headphones are handed out (often not till an hour or more into the flight) and after airline headphone are collected (often an hour or more before landing).
(b) They can be used no matter what cabin you're seated in (ie, they work almost as well if you're sitting in an exit row or BA's prerium economy cabin because you couldn't or didn't want to upgrade/uppay, my "almost" qualification being simply due to that fact that an overwing exit row might be a slightly noiser place to be than a business or first class cabin).
(c) They can be used on the ground too (when you can't find a quiet part of the airport lounge, for example!).
So I would recommned them as a backup even on flights where you expect to get headphones from the airline because you're up front.