I'm at Melbourne Airport. No Bose QuietComfort headphones in sight. So I had to make the decision: do I go with the Sony MDR-NC11s on sale or do without anything for the next 20 hours of flying?
I decided to give Sony a try. The headphones are in-ear, which is a bit of a change for me. They were also half the price of the Bose. The packaging certainly isn't nearly as nice.
I haven't bought the AAA battery required for noise cancellation yet but one immediate difference I discovered with the Sony over the Bose is that the NC11s will still work as normal headphones without a battery.
The earbuds also manage to block out far more sound on their own than one would expect.
So far so good. But I'll report again on them after I arrive in New York and I've put them to good use.
UPDATE (a Melbourne-to-LA flight later): The Sony NC11s did a pretty good job although I still prefer the Bose (even taking it account the doubled price). While playing music, the Sony were almost as good as I remember the Bose being (although I didn't have the latter for a direct comparison). For pure noise cancellation, the Sony NC11s definitely fall short of the Bose Quiet Comfort although they were still effective and made the flight more bearable. Low frequency attenuation is probably pretty close to what the Bose achieves but I found that the NC11s didn't do as well at higher frequencies. The Bose aren't perfect in the upper frequencies but the NC11s are worse.
Had I had the option and knowing what I know now, I would have gone with the Bose. But the Sony headphones did the job and made the flight more bearable. They'll last me a while (I hope) and perhaps by then, Bose will have released a QC3.