I have been visiting and re-vising QGIS periodically since I began working with GIS softwares in 2005, comparing it always to the commercial products I was learning to use in school (
ArcGIS, IDRISI, ENVI, ERDAS). Every software I have listed above has evolved greatly over that period of time, but none quite as much as QGIS.
Part of the continual growth of QGIS is in terms of UI refinement and improvements to ease-of-use and workflow. Steadily, the GUI has improved along with the underlying toolset. I feel that now QGIS is certainly the premiere free GIS software, as well as a strong contender in its own right, with lower barriers to entry than any other GIS software, making it my pick for what GIS students and professionals should be trained on first.
After graduating college, I transitioned all of my previous work to QGIS so that I would still have access to my data, maps, analyses, and work despite no longer having access to the various commercial tools I used while at university. The value of being able to "keep" my work with open formats and free tools cannot be understated.