Out of the box, Xfce is the one of the ugliest if not the ugliest DE out there. It definitely can become the most beautiful and gorgeous DE after a bit of tinkering and theming, but the default theme is not that good.
Whilst Cinnamon will run fine on many distributions, it might require legwork, and it won't necessarily play nice with the rest of the distribution. Cinnamon was developed for Linux Mint primarily, so its developers don't usually prioritise fixing non-Mint issues
Display issues with multiple monitors, particularly external output via laptop DVI/HDMI, and an odd file duplication bug when changing screensavers are the tip of the iceberg here and probably part of the reason Ubuntu have dropped Unity for the Artsy release.
Works very well for touch with Elementary OS Loki. Unfortunately, Loki doesn't handle suspend/recover very well with my X220 so I have recently switched back to Gnome3/Ubuntu. Definitely not as polished, but Gnome3 is way more customizeable.