yes, the store was down for a short period. It should be back online now. Check status.snapcraft.io for real-time info on whether there’s a known problem.
A great question. If you’re writing a standalone application such as a desktop app or command-line tool, snaps are a great solution for publishing to Linux. If however you’re writing system libraries, today you’ll want to use the traditional packaging system of the distribution: debs in the case of Ubuntu and Debian, rpms in the case of Fedora and Redhat.