Students might be reluctant to be critical of their peers. Comments may lack depth or specificity. Lacking specific technical knowledge, students might fall into the trap of the blind leading the blind. Instructors would catch content errors later in the process, essentially giving the course's technical component short shrift. Groupings of students often don't work out, and breaking these groups up can be awkward, particularly when students are collaborating on complicated projects.
International students have special needs.
Using peer review forms with open-ended and yet directed questions helps to structure student workshops and thus saves time. Having two students evaluate the paper of a third student can be particularly effective. Encouraging students to work together on joint projects gives students a competitive agenda to work together to excel. Asking students to submit anonymous evaluations, at least initially, will take away the sting of peer pressure and encourage honesty. Having students list three strengths and three weaknesses, with specific references to the text, will ensure more depth and specificity.