My broyhe have a model 4500, and it's very useful in his and my work. We are agronomist, and I think this model is tha main tool to decide pesticides application.
I have used the Plus/Delta approach/tool on many ccaosions. It is as Mark describes, an effective tool to insure everyone contributes and stays engaged. I feel tools like this or points in the process that cause reflection contribute as Mark states, but also remove the excuse at the end of the event that My opinion didn't get heard. Or, I was not allowed the opportunity for proper feedback. etc. Another point that was made, but bears elaboration, is that it forces discipline in the event process. I always make a habit of ending the day, as well as, begin the day with a bit of reflection and thoughts on next steps. I like to plant seeds relative to what has been done and what will be expected next. This process step also allows the facilitator to listen and get a grasp on any items that may have been discussed out of ear shot in any subgroups and allow the entire group to understand.