Thanks for all your kind comments! I don't want to post the follow-up without thanking all your comments.
Yes Air Serbia is basically a replication of Etihad, but of course, it fell short in some aspects, which is fine because it is their first long haul service.
In comparison with most US airlines, I actually think Air Serbia is competitive, especially towards American and United, in terms of seats, amenities, and catering. In terms of service, Air Serbia's F/As are more attentive, personal, and polished than United, Delta, and American. The difference between good and bad crews lies on if they are proud of their airlines or not. When the morale is high, the service is better.
Air Serbia's lounge at Belgrade is also better than all US airlines' lounges, especially the fact that they have a sit-down restaurant. When I requested a bowl of soup, the waitress personally asked the kitchen (since I asked for it before lunch time) and got a bowl. The size of the lounge is small, but for the amount of traffic they have, it is sufficient.
The only US airline that might be comparable to Air Serbia is definitely Delta.
I will fly the flight back to JFK on Tuesday. Maybe I will find out how the service goes when it is not the inaugural flight.
For the one intra-European flight I flew, Air Serbia is just a league above everyone else - printed menu, personalized service, pre-takeoff beverage, hot towel, and most importantly, a real business class seat.
Anyway, I will work on it tomorrow morning.
Thanks for all your kind comments!
Carfield