Not sure where to report this, but I've been playing with the attendance module and we love it. However, I found an issue. If you create an attendance activity and set it as "No Grade", then take attendance, it still creates the grade activity as 0-100 and adds 100 points to the gradebook if you use sum of grades and it affects aggregated courses as well. We are running Moodle 2.3.1+ (Build: 20120719)
It appears that the issue is with adding the record to mdl_grade_items, there is no check to see if 'grade' column from attforblock = zero, change mdl_grade_items.gradetype to 3?