I think truly Mozart was a genius and his bright and gay characteristics are well penetrated in his works. I can feel that even though I am not an expert in Classical musics. =)
Having only half day in Salzburg, we decided to visit Mozart's home. It is located in Getreidegasse Number 9. It is not a big house, and we were told that it was a typical middle class apartment in his time. You have to pay a small entrance fee, but I feel that it is more than worth the pay.
Mozart didn't like Salzburg though. That was mainly because of his bad relationship with the Archibishop of Salzburg who didn't allow much freedom in his compositions. It is very much understandable how hard life must have been for an artist who did not have much freedom in his work. Later Mozart moved to Prague, and he really loved being there. Surely Prague is a fascinating city as well. If you are visiting Prague and visiting Royal Castle, you can see a church where Mozart's Requiem was first performed.
Anyway, back to Salzburg, it is pleasant to walk around city center while looking this beautiful city. And it was a good half-day stopover for us in our way to Italy.
But I am sure that you can find much more interesting places in Salzburg other than just Mozart related places.