I think it's a good way for people to release software for Linux without having to deal with specific distro stuff (which historically has pretty much been "just provide a .deb for Ubuntu and a .tar.gz for other people to figure out").

I'm hoping that it pushes for more people porting stuff to Linux because it's a single target that gives you access to Steam Decks, Chromebooks and desktops.

I don't think it makes sense for things that aren't desktop applications such as servers or libraries, just because those tend to be open source, don't need to be that up to date and benefit from tighter system integration. I see it as something that sits on top of other package managers rather than replacing them.

For Flathub? Eh, if they turn out to be bad we can just all move to another server, we're not snap. :P I'm willing to bet that someone has already made a flatpak repo for Citra and Yuzu.