I dislike Cinnamon because it doesn't "just work" if you have multiple monitors like I do.
Apps don't sync properly on the taskbar across both of them. The only way to get them to sync properly is to disable the grouped taskbar. People have mentioned this to the Cinnamon devs for years now, and they don't appear to use multiple monitors so they don't care.
KDE Plasma works great with multiple monitors and has been 100% an upgrade over Cinnamon. Plus there's more third-party support for Plasma than there is Cinnamon.