It does not fog up and does not let water in if applied well on the face. It is perfect for surface water activities, but if you dive a little, the pressure it exerts on my face seems high, although I am not knowledgeable enough to judge it. All these are secondary and I would rate it with 4 or 5 stars, but I found a significant flaw that was not mentioned in the other comments:

The disassembly is a nightmare. The clips that attach the snorkel to the main body of the mask are very fragile, resulting in them breaking very easily. The manufacturer provides a video with the process because the problem seems to be known on the English-speaking internet, but still, I couldn't disassemble it without causing damage. I don't know if these points do not cause problems if they break, but it is unacceptable for such an expensive mask to have such an issue.

Personally, I kept it assembled for all my vacations and tried to disassemble it very carefully at the end, as it is bulky to store together with the snorkel. However, one clip broke.

It is the second summer that I have been using it, it is perfect, I have enjoyed it very much, it doesn't fog up, it doesn't let water in, you can breathe normally and you can even talk without taking off the mask, and the best part is that no sea dirt gets into your mouth like with conventional masks.
The only thing I have noticed is that when you dive, there is a lot of pressure on the face and personally, it tires me out... so I don't dive :)
Other than that, it is worth every euro and I don't regret the money I spent.

Overpriced. The breath you take feels like it's not enough for you. However, it doesn't blur and applies well on the face. Very expensive though for what it offers you.

It is not suitable for diving, but it is perfect and very easy when you are on the surface. I have let people who cannot use a conventional mask try it and they are thrilled! You can see the seabed very clearly! It is expensive but it is worth it because it is also well-constructed and provides a better experience than the conventional one.