Two things come to mind, but they’re not problems, just slight disappointments.
The first was when I realized the built-in microphone doesn’t work with A2DP, so the headphones need to switch to HFP for the duration of your speech. I just used another mic as a workaround.
The second is that the bass could be sliiiightly more powerful. My ears adapted to it quickly, so that went away after the first hour of listening. It’s not really a big deal, but still, you expect more in this price range.
As far as I can see, reviews say the active noise cancellation isn’t top notch, and that the product is rather pricey, with better ones costing less. As it’s my first pair with ANC I was just blown away with its performance, so that makes me wonder how good the others are. Reviews complain about audible hiss when ANC is enabled, but I don’t hear anything really. It just bleeps for 0.1 s when enabling ANC and silence follows.
I agree with the price complaint if there are better pairs, but from what I see, they are all either wired or don’t have active noise cancellation. In my case I was recommended these by a coworker and found a nice deal (250 USD), so I went for these and am completely satisfied. It’s one of the very few pairs with both ANC and Bluetooth, which may justify the price.
They also aren’t foldable. You can adjust the basic length, but that’s all. You get a nice sturdy case to carry it in though.
Besides this, I’m constantly impressed how long they work on a single charge. The other cool thing I just remembered is that the LED that indicates connection is small enough not to bother others with its blinking. The previous Bluetooth headphones I had (Dell BH200) had a large diode that flashed so bright it briefly lit the room at night every 5 seconds. It’s a small detail, but can definitely affect the experience.
They also have NFC in the left speaker (the right one has touch controls). As with NFC, it’s nice to have, but I don’t think I used it more than half a dozen times. Your mileage may vary.
Once you go wireless, it’s impossible to go back to wired headphones. I can’t imagine there being a better wireless pair with these features. Looks like there’s a better pair, cheaper! Bose QC25: http://www.pcmag.com/article2/0,2817,2468872,00.asp - it also has removable batteries, which is a plus, but PCMag put it in the cons section for some reason. Try googling these instead.