If you are a civil engineer or designer and know what an alignment, profile, cross section, and surface, etc. are, and you are not tasked with the setup of the program, then getting in an doing some basic tasks is not that difficult.
Where the learning curve really comes in, is the setup and adjustment of the thousands of settings. Generally speaking, Land Desktop, Carlson, Eagle Point, etc. are add-on's on top of AutoCAD. These programs for the most part calculated where geometry and annotation needed to go and created AutoCAD entities. For example, if you created a label for a profile and it needed adjusting or the text needed tweaked, you could just simply use AutoCAD commands to do this.
As a general rule in C3D however, labels and geometry are products of the information provided, and changes to the appearance of these objects are not typically controlled by AutoCAD commands, but rather by the hundreds (if not thousands) of styles and their settings. This is where I see people struggle. To change the color of a TEXT object in AutoCAD may take a few seconds, but to change the color of a Label object in C3D could take minutes or even hours to find the place to change this if you don't know where to look.