QGIS forms the front-end for a lot of our automation and processes. We use it as an input, usually by drawing areas of interest, and then triggers in Postgres fire off containers to process those areas and fill in contents of other layers. We also use it extensively in planning, surveying, and documentation. It features heavily in all stages of our product lifecycle, from viability planning through to in-life servicing. If not for QGIS we'd likely be paying someone like ArcGIS a lot of money for a product significantly less flexible and hackable. For interest this is for a fibre ISP.