I have similar feeing for Gmail (it's effective anti spam engine), google maps and google docs (which pioneered shared docs. It feels outdated on many fronts now, but it was a pioneer).
Google maps would only be a net good if the data was available under a free licence. As it is they take data from people that should have gone to a public project like OpenStreetMap.
At one point I contributed quite a bit to google maps, because it was the primary map system I was using at the time. Had I been using an OSM-based system, I would have made contributions there instead.
I ran into trouble because Open Topo does not report a stream the 7.5" series does. There's serious data quality issues that can make it not work for some applications.