How worried should we be about Omicron, the new coronavirus variant?

Since South African authorities announced the arrival of a new coronavirus variant that contains an unusually large number of mutations, countries around the world have mobilized by putting into place travel restrictions and precautionary measures.

There is much that's still unknown about this variant, Omicron. While scientists are gathering more information, the public wants to know how worried they should be.

Is the alarm around Omicron warranted? What's already known, and what are the key pieces of information still to be researched? Are there things we can do to prepare for it?...