We are not huge fans of Via Nazionale due to the traffic and noise that seem to always accompany us here. It does offer direct, straight approach to Trajan's Market in an area known as the Imperial Forum, just next to the popular trio of attractions (Roman Forum, Palatine Hill and Colosseum). On the other end of this long, straight street, you can find Piazza della Repubblica and the Termini area.
We usually take the smaller streets when strolling towards the attractions near Piazza della Repubblica and Termini Area, finding them more pleasant and less choked with traffic and noise. Or the Metro can be used to transfer to/from this area from the more central parts of the city.
Via Nationale itself isn't a bad street for shopping and there are restaurants and hotels to be found here as well. So if you are staying here, you will probably enjoy this street fine and you'll appreciate the access to important city centre attractions that come with being this close by.