The PC gamer article linked from that video gave the actual information.
Basically, as a consumer, having access to UWAs doesn't harm your machine in any way that I can tell, but they are inferior to normal Windows applications. Thus I wouldn't put the presence of that as a reason to not upgrade.
Long term, I agree with what was said about the dangers of a walled garden. That's why I use Android devices and not Apple. Particularly devices I can root! But I'm OK with that general idea of an app on Windows as long as I can "root-interact" as well.
From a technical and security perspective I actually like the WinRT interfaces for programs better, as you can definitively KNOW what types of things they are allowed to do, while normal Win32 (or .NET, same concern) applications can do anything they like. So I'd rather have most programs with app-like restrictions (in a domain you can do this with group policies, but that is super-advanced), but be able to run certain root-like features as well, and mess with the install directory, etc. Some of the decisions are moronic, like if you couldn't choose to install outside of program files. Idiotic decision. Basically, the platform isn't advanced enough yet.
