AU is not a very functional organization. Does not really matter.
I would say that AU have been a great success, it have made the African continent much more stable, thanks to their hostility to coups, support of free elections, willingness to deliver soldiers against local uprisings and peacekeeper. Africa have not been as stable and peaceful as now ever. Of course I can't see what AU can do in Haiti, so this is a purely symbolic act.
How do we know all that progress has been due to the African Union?