Just thought I'd make sure everyone knows:
Bose headphones are on sale at Amazon right now. Just picked up a pair of QuietComfort 25s for $179 (usually $279). Might be good for those of you who travel and play games on the plane / bus / train frequently.
I'm a big fan of the QC20. They may not be the highest fidelity headphones, but I find them very comfortable to wear for long stretches of time since the fit is very different from IEMs, and the active noise cancellation is very effective.
I don't like the passive isolation you get with IEMs that reduce the ambient noise by a similar amount. Feels like I'm underwater, and the cable transmits a lot of noise if anything rubs against it.
Being able to press a button and hear your surroundings or have a conversation, while still retaining a bit of low frequency noise reduction, is really convenient too.
The only inconvenient thing is the battery pack. It's not huge, but it can get in the way if you're using portable devices, and you do have to remember to charge it. Worth the trade-off though, in my opinion.
I don't find the QC25 to be quite as comfortable as they're much larger and heavier than the in-ear design of the QC20 (but still very light relative to other circumaural headphones) and the noise reduction is not quite as effective either since the passive isolation of that design is lower.
Because they go over your ears, there's a slight pressure when you switch noise cancelling on, but it's not as bad as NC used to be. Less of a problem for me than the physical pressure of larger/heavier headphones.
Running off a single AAA battery is great, as it goes for something like 30 hours and the case has a space to keep a spare. I use rechargeable batteries with it (get Fujitsu pre-charged) so that I'm not buying a pack of batteries a month, but it's great having the option of walking into any convenience store and picking up more if you do need them for some reason.
It's one of the reasons I've been hesitant to upgrade to the wireless QC35. The wire is inconvenient - especially with most new phones requiring adapters - but I don't like devices which have fixed rechargeable batteries, rather than batteries you can swap out for a fully charged spare when they die.
I have higher-end headphones too, however I find the complete absence of other noise to be far more immersive when gaming and end up using Bose more than anything else now.
I could never go back to open-back headphones like the higher-end Sennheisers. Once you've been using NC headphones for a while, things like fan noise, AC, road noise etc really begins to stand out.
This video review did a great job demonstrating the effectiveness of the noise cancelling. (wear headphones)