So far, even taking lag into account, this looks less lethal than SARS and mostly affecting people already in bad health, although way easier to spread. For example, the relatively young woman hospitalized in Sweden today already is doing "quite well" and it was mostly a coughing episode for her. The more widespread epidemic than SARS could still be influenced by being formed in a city larger than London, but in terms of that there's no need for complacency. Australia have taken it seriously by quarantining their evacuees on an offshore island. There's a fair bit of naivety in just giving stay at home-advice like this until we know more about it. This feels a bit like playing around with the lives of people in frail health.
Hopefully the Chinese military response is just in order to be a controlled operation rather than a cover-up of something a lot worse in terms of how many who really got infected in the Hubei province. With the poverty and the inequality of medical care still around in many areas of China, it could be a really devastating scenario for them if say 10 million Chinese take ill. Hopefully, this is just them playing it safe.
Still, if some serious pandemic worse than this would originate in China, this could be a very useful drill for the whole world in order to limit effects.