Sacher has a very long Tradition in Austria. I would put the Sacher as the top hotel in Salzburg in the City Center. Main Shopping area and restaurants are very close by, litteraly just accross the river.
I had a single room on second floor. The room was decorated very traditionally (typical Austrian), long carpets, nice flat TV and very good bed. The only problem encountered came in the morning as the windows were in direction to the street. For people who don't sleep well with noise outside i would recommend booking a room towards the river (anyways preferred for tourists due to the great view on Salzburg)