I'm going to copy my response from /r/Linux:

The idea behind KDE Neon is to combine a stable base with rolling updates for KDE. That's somewhat novel; it's possible on OpenSUSE (Leap with an additional semi-official OBS repository that has the latest Plasma 5) but it doesn't seem to be the norm elsewhere, so it's nice to have another option for that kind of setup by offering it on Ubuntu. (It was previously possible with Kubuntu PPAs I believe, but this being official makes it nicer.) What are the problems with it? That it's based on Ubuntu and doesn't offer a similar thing for Arch or OpenSUSE. As I mentioned, OpenSUSE already has something similar as an option. And it doesn't make sense for Arch; they already offer rolling updates for KDE... As well as the rest of the system, because the point of Arch is to be rolling. To make a "KDE Neon for Arch" would require taking the rest of the system and getting rid of the rolling release model while keeping it for KDE. That obviously doesn't make sense. There are some other distros where this could work that are getting left out. They could have the latest rolling updates to KDE backported to e.g. Debian stable. But can they be expected to do this for all distributions? KDE is already available in all distributions. This is just offering a particular release model. I understand why they would focus on one distribution, and go with the most popular (desktop one). What's the other problem? That their reasoning for basing it on Ubuntu might kind of be taken as an insult to other distros. Maybe it's not worded in the best way but I'm not too concerned. It's made by the guy who used to be involved with Kubuntu, so I understand why he'd stick with what he knows.