Use the data contained in the comment boxes of a team's list as a rich source of assessment information. You will have a record of the degree to which students applied criteria to their rankings, the logic they used in resolving equally strong justifications for a ranking, and even their reflections on their work.
If you would like to assess how student opinions, attitudes, or beliefs have changed over the life of a project, you can have your students rank a list at the beginning of the project and again at the end. After they complete each ranking they should make a printable page of their list, then copy and paste that report into a document that becomes part of a portfolio.
Using your Teacher Workspace, you can make comments, ask for information, and enter your own reflections in a comment dialog between you and each student team.
At the beginning of a project, you might ask your students to rank what they think is important in assessing the project. Their data will provide you with a good starting point for discussions about assessment.
Lists that are sorted according to objective criteria can be assessed directly. If you want students to self-assess, you can add an "answer key" team to the project and sort that list in the correct order. The correlation of students' lists to the "answer key" list will give a good indication of how close each team was to the correct ranking.