HERE is pretty damn good these days on Lumia. One big update behind the scenes has been less of a need for actual software updates for Lumia phones to get updated maps.
Nokia also moved from needing to update the whole regional map when map update is pushed, to them being able to push a single small update that just adds/fixes couple of streets and you wont need to update your whole ~1GB of map data in a result.

Though again lets remember that we are talking about map data provider here. It's another story how it will be all implemented on Jolla.

Nokia's HERE geared towards car manufacturers is built using Qt btw.