Just seeded about 24 hours ago and the existing grass has benefited by turning a beautiful emerald green. Soil looks richer and healthier too. I am hoping for great results. Though too soon to tell. The seed seemed a little old and dry however.
Read about Black Beauty grass seed in an article in the NYTimes where it was recommended. Used it both to overseed areas and to seed a bare area. Both areas have done well filling in with lush green grass. So far seems to be better than the seed blends I have tried in the past.