I was really hoping all the people leaving because of Eclipse would cause DA to atleast bring back the switch function. But, this is here to stay. Here's everything I have a problem with (so far):
All deviantations in my notification watchlist are in packets for each user. You used to just see each pic that was recently posted, now you have to click on each user packet in case they uploaded more than once (but, if you go to home, you can views them individually).
Cover images for literature posts are gone. Those Death Battle banners can now never catch your eye again. It's just a generic thumbnail now, not something personal to the user.
Previews for images has been CROPPED. You can't see the whole image until you click on it, just like Pixiv. This will cause users to overlook images and there's probably details being removed.
And the worst... INFINITE SCROLL WHEEL IN GALLERIES! Some of us have thousands of pictures and this memory munching feature is terrible. Bring back pages.
The only thing I like about is Eclipes is that they finally fixed the "back" function. You'll finally go back to where you were without any effort. But, they didn't need to break down the website for that.
Other things I can get used to, cause I don't use this website for much. Others go all out with HTML. But... it's a chore to do anything now...