The system determines whether a rocket is actually going to hit something important (civilian structures/towns, factories, army bases) and only then shoots. Also, statistically if a grad/qassam hits it causes damages of at least several hundred thousand NIS (not including insurance). In short? It's okay to feel good about the system, absolutely no need for the "BUT" that comes after the "Great".
Rohani: Nuclear deal achieves Iran's goals (AP)
from the article: Iron Dome successfully intercepts Gaza rocket for first time