I lived in Armenia for several years and Ankyun was my favorite restaurant for non-Armenian food. It was easily the best prepared steak in town and the Italian food was also extremely well done and clearly indicitive of the chef's training abroad. The prices are a little expensive for Yerevan, but overall extremely reasonable. I would recommend the place without hesitation to all visitors.
As another reviewer has mentioned, the restaurant is extremely small and it is very wise to call ahead and make reservations.