I collect headphones. Not intentionally, perhaps. But as my headphone box attests, I collect them. I head Sennheiser, Bose, Sony, JVC, Altec Lansing, Ultimate Ears, Grade, and many more. Some I like, some I hate. A few I gravitate toward repeatedly (like the Sennheiser HD600s for home listening, or the Bose QuietComfort IIs when flying, or the Ultimate Ears for the gym or mowing the yard).
I can't really defend my collection. I am not sure I can even explain it, except to say that (with the possible exception of the Sennheisers) I'm always wondering if there's something better out there...
Anyway, I got a pair of these Sennheiser PXC-310 phones to test. Now, I own a previous model in this series, the Sennheiser PXC-250. Those are small and quite comfortable, and the sound is very good. But the noise cancellation is so-so (owing the small earpads and on-ear design).
By comparison, these PXC-310 phones have bigger earpads. They are still ON ear (not over the ear, like the Bose), but ON ear. The fact that they are bigger results in better noise cancelation than the PXC-250s. BUT, and this is a BIG but, the fact that they're bigger and they're ON ear means that with extended listening they start to bother me. It's not terrible, and for an hour or two, I'm fine. But eventually, I find that bigger muff on-ear design starts to give me a headache. I don't get that with the over-the-ear Bose (my go-to phones for airplane listening, meaning they stay on for hours), nor with, for example the Sennheiser HD600s (also over the ear).
On the other hand, the sound quality of these headphones is better than the Bose: More neutral, and, in contrast to the pains induced by the physical construction, less fatiguing for anything approaching serious listening.
The Bose also don't offer bluetooth connectivity. I found the bluetooth on these worked well. I own a previous pair of bluetooth headphones, the JBL Reference 610 phones. These work as well as those, and I like the sound of these better. I also like the aesthetics of these better. Until I obtained these, the JBLs were my headphones of choice for bluetooth listening. Now they're in "the box" and these Sennheisers are my choice when bluetooth is being used.
If you're asking whether bluetooth is worthwhile...Don't think of it as a way to work at your computer or near your bluetooth enable ipod without a cord. Think of it as a way to walk around your house with a good sounding set of headphones talking to your PC or mp3 player in another room. Once you start using them this way, you'll love them...
Overall, these are very good headphones. I am very happy with the sound, especially for so-called travel headphones: Neutral, and not fatiguing. Much better than heavily hyped (and expensive) competitors such as Bose. The active noise cancellation is good. It isn't as good as over the ear headphones, which combine active noise cancellation with the noise isolation that type of design offers. On the other hand, these look a lot less massive (and nerdy) than many headphones with that design. My main complaints would be that the on the ear design can be uncomfortable for very extended listening (although an hour or so is fine), and that the price is fairly high. But try them yourself. If they're comfortable for you, you can't go wrong with these.