I have been encountering a lot of Plus/Delta activity at the end of my meetings and projects. Basically it is an informal feedback mechanism. A chance to communicate 1) what was good about the meeting and 2) what may need to be changed in the future.
I can appreciate the sentiment. Just having a project or meeting leader ask for the feedback is a great step forward in improving processes. One of my group leaders took it a step further though when applying it to tasks or projects.