The old mobile maps were frustrating to use. Very data hungry and high latency and with quirky UI bugs. It was very much a translation of the web app meant for desktop use on low latency broadband to a mobile app with only a few tweaks. For example, pinch zooming would work surprisingly, by zooming the low-res tiled image and then effectively translating into a button press to zoom in/out one level, leading to a very frustrating and clunky experience that essentially removed any advantage of using multi-touch gestures over just pressing the zoom in and zoom out buttons.
Google has not only fixed those problems, they've improved the experience several times over. It's fabulous. It's faster, it's responsive, it's seamlessly interactive, it's a pleasure to use.