QGIS is a free (open source) popular, geographic information system whose community of global volunteers has been improving its base functionality and extensive capabilities since its inception in 2002.
From labeling to analysis, this tool allows its users unprecedented freedom.
Note: There are too many flavors of Linux (RPM and DEB), and most of them hold older versions of QGIS. The best way to make sure you're downloading the latest version of QGIS, visit the official page here and scroll down to "Linux" section.
Straight out of the box, the current iteration of QGIS is a powerhouse. Domain-specific tools, vector tools, raster tools, and raster/vector tools are conveniently labeled and organized for beginners and advanced users alike, as is the entire interface. Aside from the essential functions, there is also a library of more than 500 plugins (and growing) in the repository.
Perhaps the best aspect of QGIS is its ability for data consumption. You can get as detailed as you need (and probably more accurate than you need) for projects that may require a high level of subtlety. QGIS is excellent for multi-location projects with different weather conditions or construction on a dodgy terrain.
Each plugin gives you the ability to drill down into your chosen tasks, allowing you to customize the priorities of each project as needed.
QGIS is also improving at a rate that is putting all of its competition to shame. The community around QGIS is more loyal than any other. The usual shortcomings that usually accompany open source efforts do not exist here. QGIS is exceptionally intuitive and does not require a higher level of computer knowledge than commercial GIS packages. Users have access to a more helpful "customer service department" than commercial companies as well.
The forums based on QGIS are thorough, and the volunteer coders pride themselves on solving problems.
Overall, QGIS is an excellent choice for any AEC professional who needs a complete, future-proofed software. If you are looking for an intuitive, highly detailed platform that is flexible enough to work any project, then you have come to the right place. Once you add the library of plugins and the resources of the community to the equation, QGIS is a no-brainer.