The midpoint Sun/Moon is a most important midpoint. Not just because it is the point in the middle of the lights in the sky. Also, because this midpoint symbolizes the marriage of heart and soul, the crossing point of spirit and soul and the integration of body and soul. An aspect with this midpoint offers insight in the heart desires of a person and what this person really wants out of life.
The progressed midpoint Sun/Moon, I thought, might be related to a changing and growing development of the hearts desires by transits of the moment or by aspects with the natal chart. I give some examples below.
A few days ago I illustrated the importance of the progressed chart using the progressed chart of Obama. This progressed chart has prominent placements for Saturn and Pluto, the symbols of government and policy. People grow and progressed charts show us in what direction.
In a progressed chart the positions of Sun and Moon change, of course, as the progressed chart shows positions of 1 day = 1 year later. Sun/Moon also changes with the rest of the chart. When I found out that on my wedding day transit Jupiter was conjunct the progressed midpoint Sun/Moon I was encouraged to find out more about it. On a first working day after a period of rest, Pallas was conjunct my Progressed Sun/Moon. I had to live in a pattern again...
Joe Biden had T Pluto at 29d22 Sagittarius semi square his progressed Sun/Moon in 14d16 Aquarius on Election Day. Pluto crossed the progressed Sun/Moon midpoint several times in the last months of 2008. He was confronted with the death of a family member and his son left for Iraq in an intense period of political confrontations! It was transformation time.
So: don't just look at the natal midpoint Sun/Moon but have a look at the progressed Sun/Moon midpoint, too. It might be a usefull tool to find or select a perfect day. Mine will be on January 6, 2009: Venus opposition Sun/Moon. Sometimes New Years speaches are real fun, I guess.
BTW As the Moon moves quickly, the Sun/Moon midpoint moves about 8 degrees each progressive year. When planets like Venus or Mercury or Mars move over this midpoint, it won't have a long lasting effect.