BaldEmu -- I know there are a whole bunch of threads about this spread over various forums, you might want to search.

I have the Sony NC-10's (earbuds) and NC-20's (headphones). They're OK on the plane (I find it hard to sleep with them on, but it makes it much easier to hear a movie), but the NC-10's are great on the bus, which I take every day -- filters out the bus noises and the inane chatter about high-tech stocks, which seems to be the only topic of conversation on mass transit here in Silicon Valley!