As far as I understand, one of the purposes behind MSAR was to refine and upgrade the AUG. Ergonomically and esthetically the MSAR is probably nicer than a typical Steyr AUG. The parts on your stg77 are coming off the same machines and parts bins as all other guns Steyr ships across the world, which is to say that you get a functional, reliable, and durable gun. Could flashing be better taken care of, could the sharp edged safety be broken smooth, could Steyr put more attention to detail or at least do some basic upgrades? Definitely.
You have a rock solid product backed up by a solid company and an outstanding warranty.
Of the things you listed only the ejection port cover sounds off I'm not sure what's going on with your port cover, call Steyr and they'll take care of it.