If you are in an urban area (especially at the time it was introduced), it will really improve things, mainly because GPS* signal reflections in urban areas disrupt proper positioning. It won't put you into another continent but it tends to be around two magnitudes worse, especially when you're moving (from ~1 meter to ~100 meters). The fact that multi-band GPS is now common does reduce this problem, but this is still helpful in dense areas with high skyscrapers that can still attenuate both bands.

* I'm using GPS here as shorthand for all GNSS systems (including GLONASS and Galileo).