I have used the Bose QuietComfort 2 headphones for many years (they are now broken, both arms have cracked) and I replaced them with some Sony in-ear NC buds.
The Bose cans still work well, only the arms are broken, but the Sony NC buds beat them in every way.
Better noise cancelling.
Still work as normal buds without power (Bose QC2 only work with power)
Much more comfortable for long time use (>12 hrs)
Comes with different size bud cups
Much, much cheaper
Other in-ear NC buds may be equally as good.
Bose is very overpriced.
I won't go into hi-fi reproduction quality as that's not why I bought them either. Flying international every week for six years is all about try to reduce the deafening roar to a bearable level.
dot.zen