The Edit Summaries tool analyzes how many times a user has included an edit summary with their edits. High edit summary usage is often seen as an effort towards collaboration.
This tool can sometimes timeout for very prolific editors. If it does, try using the form to limit results to a smaller date range.
The Summary section gives your basic totals, as well as edit summary usage within major and minor edits. In this context, major edits are simply edits that were not marked as minor. XTools does not take into account the actual size of the edit.
This lists the total number of edits and number of edits with summaries, broken down month by month.