I work in the mass appraisal space, and I use QGIS all the time. The professional alternative is ESRI's ArcGIS.

A lot of shops I know (private and public) will use ArcGIS still, but I'm noticing an increasing number of people (particularly younger researchers/analysts) who are exclusively using QGIS.

QGIS is powerful and full featured, but it is admittedly a bit rusty around the edges, especially when working with very large datasets. If they keep working on fixing some of the sharpest edges I think it will go on to have a good future. Just in the past few years I've noticed significant improvement.

In many ways it feels like Blender -- long ignored and dismissed, but slowly but surely improved over time, and then suddenly became quite a big deal.