What I've found is that beginning students, the sorts of people who take survey courses, are ill-equipped to read these materials and often profoundly misunderstand them.
History is a difficult and subtle craft.
Throwing primary sources at a beginning student is a bit like giving him a tree trunk and telling him to make a cabinet. That's the reaction of a tourist in a foreign land, not of a historian understanding the material. I hear it argued frequently that we should have students read in the primary sources so they can get a taste of what professional historians do, but this argument is specious. Reading Vergil, the Song of Roland, and Chaucer gives them the flavor of only one kind of history. All this probably only reflects my own current uncertainty about how I use primary sources in my own classes.