I fly long-haul flights frequently and have used Sony's in-ear noise canceling headphones for the last two years. They work very well as long as they are positioned correctly in the ear -- this requires frequent re-adjustment during flights which is a bit of a nuisance.
The Sony MDR-NC60 headphones are an around-the-ear design. They are far more comfortable than the in-ear designs, and I find the sound quality to be pleasant and relaxed. With an iPod, I find that setting the EQ to "reduced bass" results in the most pleasant experience. The noise canceling function works very well. Overall, I am very pleased with this purchase. According to the reviews, there are several competitors (notably Bose) who produce a "better" headphone, but their prices are outrageous. One thing I like a lot about the Sony is that it runs on a single AAA battery (which can be purchased anywhere in the world very cheaply) and that the headphones can be used even if the battery is flat. Remember, if you buy something like the Bose, you'll have to travel with a battery charger, and you'll have to pay for an expensive battery when the supplied battery finally dies. In other words, the cost of ownership on the Sony's is superior. This is just my personal preference of course, but as a seasoned traveler I like to think I know what I'm talking about!