I’ve used the previous versions that were just a modified Gnome Shell. It was good. They made some common sense improvements. Pop!_OS in general is a good distro for their machines. It comes with their custom hardware drivers pre‐installed (you can install them yourself in other distros). I have not tried the new Cosmic desktop environment. It’s built from the ground up by them but it’s nothing revolutionary. From what I’ve seen it’s like their previous modified Gnome Shell. Some nice tweaks, window management features almost no one will use, keyboard shortcuts you can probably set in other DEs, and hardware management features that might only work on their machines. They’ve also reinvented the wheel with their own Cosmic versions of some basic desktop apps like a file manager. It’s written directly for Wayland, so no option to run in X11 or X11Libre.