From what I saw Cosmic has a lot of potential and looks pretty sleek too, right now I'm using KDE it's a great desktop, but now that I have a second monitor it randomly crashes on me, I think I'll switch to Cosmic when it reaches beta.
I've been using it on my Fedora laptop for the past week or so and it's really nice, even in alpha 1! Can't wait to see how it turns out fully finished!