The audibility varies from person to person, so the evaluation is purely subjective.

Positives:

-Very nice simple and minimalist design, good quality plastics and premium feel with foldable headphones for volume reduction.
-Perfect sound, you can hear every detail in music or gaming. Sennheiser has done a great job with the sound, anyone who deals with sound knows the quality of the sound in this company's products.
-Satisfactory ANC which, however, deactivates itself when you speak and you can hear yourself.
-Infinite battery life of 30 hours and type-C charging in just over 2 hours (2 hours and 20 minutes measured from 0-100).
-Qualcomm aptX and aptX Low Latency codecs, Bluetooth 5.0, so there is no delay in the sound.
-Smart Control app. With the previous firmware, I had a problem recognizing the headphones, but with the latest upgrade (5.5.1) it has improved, although sometimes they do not connect to the app even though they are properly connected to the phone (about 1 in 5 cases).
Through the app, you can do the following:
1. It has a simple equalizer with various presets (it also has custom presets).
2. Sidetone (how much you hear your voice in calls).
3. Sound Check (with an account on Sennheiser).
4. You can see the battery percentage.
5. News from the Sennheiser community.
6. Option to save equalizer presets with an account on Sennheiser.
-Multipairing devices (laptop, mobile). If you have a call on your phone, it prioritizes the phone.
-The microphone is good by my standards, but I read in various reviews that it is very mediocre compared to the competition.
-It comes with a jack cable (2.5mm to 3.5mm) that allows you to listen without using the battery and with slightly better performance. Be careful with the jack that connects to the headphone, when you insert it, you have to turn it so that it "clicks" because if you don't, the sound will be distorted.
-It comes with a fabric case and the headphones fold to reduce volume.
-Ideal for travelers who do not want to hear external sounds, for example on an airplane, with the option to disable ANC.

Negatives:
-Many buttons, all on the right headphone, which takes some time to get used to.
1. On/off and pairing button (with one click you activate or deactivate ANC).
2. Volume up/down button (pressing it in the center shows the battery level).
3. Button with a variable controller like a joystick where you change tracks forward/backward (pressing it in calls answers or if you are listening to music, it plays/pauses).
4. Voice assistant button.
-The on/off button needs to be pressed for 1-2 seconds to turn on the headphones, if you press it longer, it enters multipair mode and searches for devices, so it is a bit confusing.
-The ANC, although satisfactory, does not work miracles. You don't hear loud and continuous small sounds (e.g. the engine of an airplane or ship), but it's not Bose, so high noises or people's conversations near you will still be audible. It is only for ambient noise.
-The fit of the headphones is somewhat tight at first and the ears hurt, but after a few days, it gets better. You can place them between some books for 1-2 days to loosen them a bit (tip from the official website of the company).
-The earpads are very thick, resulting in a smaller surface area available for the ear, so they are not suitable for large ears. In essence, for normal to large ears, the headphones function more like on-ear rather than over-ear. It is not memory foam, and that's why it's difficult to get used to them in your ears.
-In warm climates, ears sweat and heat up, but this is an issue with many over-ear headphones.

Is it worth buying them?
For me, a big YES. Very good and clear sound for headphones worth 200+ Euros that are sold for 100 Euros due to high competition, good ANC, long battery life but with a steep learning curve to get used to the many buttons.

I hope I helped, and if so, please give it a like to see how many are interested in these headphones.
Thank you

They are very good headphones with very good sound.
The noise cancelling, although good, could be better for headphones that cost 100+ but it's okay. For the office where I use them, they are fine. I haven't tried them with public transportation, but I imagine they will do a good job based on what I have seen so far.

The 4 stars are only for the ear cushions.. They could be a liiiittle bigger.. a little bigger.. They can be worn for several hours of continuous use, but after a while you feel like you have them on.

Overall, they are very good headphones and with a few minor adjustments, they could be much better.

EDIT 6/13/2023: The noise cancelling is a joke compared to other headphones. Compared to Anker headphones (life q30), they do nothing to isolate the sound. As I mentioned above, they do their job in an office setting, but I don't see a huge difference anywhere else. I would definitely go for something else because the ear cushions are not good enough and need to be replaced as someone else mentioned in the comments, but that's probably what is lost after the noise cancelling. If you want them for simple use at home, then they do their job, but if you want them for noise cancelling, I don't think they do their job well

Well!
I have spent a lot of money on headphones. From gaming headphones to cheap ones, from Razer to Bluetooth and wireless headphones, and so on and so forth.

I made this purchase a year ago, so my opinion is well-informed.

POSITIVES

High volume and very good bass.
Not perfect, but very good.
Quality construction, durable ear cushions even after sweating and over time.
You forget to charge the battery. With daily use, they last for three weeks or more.
The buttons on the right side are user-friendly. They are used for switching songs, accepting and rejecting calls, adjusting volume, and the power button.
They are large in size, they open up and fit even on the biggest head (mine, for example).
The ears fit inside the headset, making the surrounding environment quiet. When in call mode, the noise cancellation is turned off, and you can hear everything around you as if you're not wearing them.
Very comfortable fit on the ears!!!
For the money, it has very good construction since it can rotate from whichever side you want without breaking.

NEGATIVES

They are not suitable for summer in Greece, guys!!!!
They are not for running or the gym.
Also, they are not for extended use. AND ALL OF THIS IS BECAUSE THEY HEAT UP YOUR HEAD.

In all three cases, the ears sweat and your head gets touched by the headsets.

For the money, these headphones are the best!!

Today I got them, so I don't have an opinion about everything at the moment BUT

They have very good sound and bass, much better than my old headphones (razer kraken)

I have been using them for 5:30 hours and they still have 12+ hours of playtime on Bluetooth, which is a lot of hours

For these 5:30 hours that I have been using them, I haven't felt any discomfort in my ears or anything like that

As for the build quality, I won't say anything special because I'm not an expert, but they look good

The voice cancellation is mediocre, but the headphones cost 100€, we can't have it all

The weight is somewhere between light and normal, personally I find their weight very convenient

Also, there is an app from this company that allows you to increase the bass significantly

For 5:30 hours of use, they are worth the 100€, if they have any problems in the future and I remember that I left this review here, I will inform you

Edit: after 10 months, I have to say that nothing has changed! They are still very good