Having flown Paris-Athens-Paris, I think Aegean business class is good ... and these upgrade coupons are a real plus.
Good points : nice staff on board, good food, nice red wines
Bad points : no priority boarding in Athens, priority luggages seem an unknown concept to Aegean, sparkling wine served after boarding is not champagne and is absolutely awful.
Worth noting that the LH lounge in Athens, although smaller, offers a much wider range of food and alcools than the A3 one. It was also much more crowded when I was there. (10h-13h)