I have had these headphones from Bose for about a year and a half, and I have absolutely ADORED them. They have been a great experience, not only for the listener but for the people around them. Here I will review these headphones, and list some pros and cons too.
The sound quality of these headphones is amazing. After listening to some of my favorite songs on them, I have heard little details that I have never heard before. The "Surround Sound", although not true surround sound, is still incredible, giving me the feeling that I am right with the performers standing in the studio. And, I don't even need to switch applications to change the music or lower/raise the volume - the QC35 II headphones have built in Alexa voice control.
The main gimmick of these headphones is the noise cancellation technology. I think the noise canceling on these headphones is excellent. Not only do they block loud droning sounds like an airplane engine or a blender, but they also block out footsteps, loud voices, and other things like that. It's nice to escape the loud sounds of the city and entering your own little world. This ability is especially useful now that we are all working at home - if any of your family members are watching TV, conducting subwoofer sound tests, or typing on obnoxiously clicky keyboards (cough, Kailh Box Jade, cough), these headphones will be a lifesaver.
If you sweat a lot, I wouldn't recommend these headphones as the leatherette material is not very breathable. In hot weather, these headphones become uncomfortable for me after an hour or two because they seem to engulf your whole head - which is good for noise cancellation, but not for breathability. Additionally, this headset is extremely expensive, coming in at $300. Since there are perfectly adequate, albeit not noise-cancelling, options for $25, this is a bit of a tough sell.
Overall, I really like these headphones. Although the price is quite high, these are my daily driver to help get work done and block out outside noise during shelter-in-place, and will continue to be useful even when we get back to school or offices. The noise-cancelling is wonderful for planes, school, or office work, the sound quality is crystal clear, and the experience overall is one of my favorites from a headset.