I used COSMIC for a while and really liked the core DE. Being able to easily move between stacking and tiling is great and the workspaces work well. The new multi-monitor stuff sounds good.

I do not love the included apps. The terminal was ok but a bit of a memory pig. It is Alacrity based. All early days though and of course other apps work great with it, though with mixed UI.

Early versions leaked memory but apparently that was related to a bug in Glibc that they have now worked around.