We visited Serbia only as a "transit" country traveling from Ljubljana all the way down the Balkan Peninsula towards Skopje in Macedonia.
The only one day stop we had was in Belgrade. Unfortunately, the city didn't impress us much, to find out why, have a look at the post about the Serbian capital below.
Having said that, seeing only one place simply isn't enough to tell what the country is really like. Serbia has an amazing potential for travelers who love off the beaten path destinations, that's why we're planning to return and visit other Serbian cities and spectacular, unknown natural wonders such as Uvac River Canyon and Davolja Varos rock formations.