This article seems to suggest that it is likely about as communicable as SARS, but less lethal (about 9.5% for SARS vs about 3% for the new virus.) If it follows the SARS epidemiology pattern we would expect a little over 200 deaths before it gets under control. Definitely worth taking action to get it under control, but nothing to panic about.
The caveats is that we have to rely on Chinese government figures so they may be underreporting the number of infections/deaths, on the other hand it appear that very swift action is being taken against it, so it could be significantly more or significantly less than my estimate.