Its hard to say. There are a few ragequit posts, but most of the complaining has been fairly positive -- for every quit there are 20 or something suggestions to make it better.
and a lot of people play it out and put it down until the next update. So you can't look at the online numbers etc to say they are gone for good, rather than just not playing right now.

About all you can say is some people quit, and more people seem to dislike the mist & spastic terrain than praise it. I don't like the mist much, but I don't hate it enough to quit either. I beat the boss and have few incentives to go back into the fog... I can enjoy building without too many more trips until I run out of marble. I don't have a tone of incentives to go back to the mountains or meadows either ... which is fine.