OK, so they look almost exactly like the pair of QuietComfort 2s you used that one time you had enough miles to fly business class, and they still cost $US300, but you'll have to trust me: something's changed.
Anyone who's had much exposure to Bose's bulky QuietComfort 2s, and smaller, cheaper QuietComfort 3s knows the story: they cancel noise pretty well, and they sound pretty good, though in the last few years—QuietComforts have been around in their current incarnations for a surprisingly long time—other companies have stepped in with products that do the same thing, cheaper. So! Bose has two options: Go low, or, you know, improve the product. With the QuietComfort 15, which will replace the old old old QC2 starting tomorrow, they've gone with the latter.
From a design standpoint, this is a familiar product: It's hard to find any external hardware changes aside from a new LED indicator and a slightly changed curvature on the headband. Likewise on the sound, which is perfectly adequate, but won't blow audiophiles away. The noise cancelling, on the other hand, is a different story: it strips out low frequencies way, way better than the QC2 or QC3, to the point that typical airline noise (simulated in my tests, but definitely loud) becomes almost imperceptible. Wearing these things sounds almost like you're wearing a second set of Bose's old models. Pending fuller tests, I'd say it feels like this is a healthy upgrade for the QuietComfort's target customers: guys with suits and belt-strapped iPod Classics, and airlines.
That said, they're still fairly bulbous, and probably deserved a redesign, since this shell's been around for nearly a decade. That, and the price: it's still going to be $US300, but since these improvements are fairly subtle, it'll be hard not to feel a little ripped-off at the register. [Bose]