This is without a doubt an authentic restaurant. This place has been chosen by the organisers for one of the nights of the week long event for 80 people; so it definitely was not an easy task for this taverna's staff.
The food was very tasty and plenty of it, with the starters being served in the Greek tradition of sharing the plates (meze). The service was nothing out of the ordinary or exceptional; the staff was fairly quiet and not very chatty, but were quick in bringing over whatever we asked for; so there is nothing to complain about.
I would be interested to have dinner in a more casual environment, so as to test their menu outside of an organised event. Based on this first experience, I would assume they would not disappoint.