Great place. Beautiful Old City. Lots and lots of great restaurants, places to see, amazing nature. All within the city. No need to rent a car, cheap public transportation and taxi services.
Nothing special, city center is a large place, it is ok for a evening walk.
Sibiu is surrounded by mountains in the center of Transylvania. It has a beautiful and wide main square, the Plaza Grande, with palaces, aristocratic buildings and cafes, most of Germanic architecture. The old town is very well preserved with the High part and the Low part of the city, with its churches, towers, old houses and museums. Also from Sibiú you can meet splendid places like Corvinolor Castle in the town of Hunedoara; or Alba Iulia, an old citadel that holds many treasures such as the Hall of the Union, where the merger of Transylvania to the kingdom of Romania was proclaimed in 1918.
Sibiu is one of the big cities in Transylvania. The old town is really beautiful, especially in winter when it's covered with snow. Two days would be a good enough time to see all the attractions but it would be good to stay longer and enjoy beautiful Transylvanian city.