I tried the new headphones at a demo in New York City and was impressed. The earpieces employ a cushy, memory foam that conforms to your ears nicely, and they do a better job than you'd think of passively shutting out noise (on-ear models tend to let in--and leak out--a fair amount of sound). The headphones seem very comfortable, at least in my brief listening test.
The QuietComfort 3s feature the same fold-flat design of the QuietComfort 2s and come with a protective carrying case that's just a little smaller than the one that ships with the larger preceding models. Aside from the more compact earpieces, one of the big differences between the two headphones is the inclusion of a proprietary lithium-ion battery with the new model. That's a nice plus--the battery slips out of the headphones and into a compact travel charger that fits right into a wall socket, obviating the need for annoying wires or cables. Bose says you'll get about 20 hours of battery life before you need to juice up. (Extra batteries will be available for $50 a pop.) The charger also fits snugly in the headphones' carrying case, and you'll be able to purchase additional chargers compatible with international voltage requirements.
Companies such as Sennheiser make noise-canceling headphones that are smaller and cost much less than Bose models. Apparently, the feedback Bose has gotten from consumers is that some people prefer these smaller designs, especially for everyday on-the-go use rather than just airplane travel. In other words, the company hopes to get more people walking around the streets with these headphones. To that end, the company also showed a $40 adapter that lets you use the QC 3s as a stereo headset for multimedia cellphones, such as the Nokia N91 or Palm Treo models.
The older, larger QuietComfort 2s remain available for those who want an over-the-ear design, while the QuietComfort 3s are available to consumers looking for something a little more discreet. Eventually, however, I think the company will have to drop the price on the QuietComfort 3s and QuietComfort 2s to $299 and $249 respectively. Three hundred and fifty bucks just seems like a lot to pay for headphones, even if they do come with a rechargeable battery.