Most of the ideas about Progesterone having negative mood effect were, effectively, from dispensations that are much less pure than the bioidentical, micronized versions available now. It's actually 'lack' of adequate progesterone or fall of its levels that is associated with mood issues. Some doctors swear it's not necessary, but chemically my body really did not feel right without a complete hormonal profile.
I just started mine a few weeks ago and there is a BIG difference in terms of my general sense of well being. Extremely pleased that I went for it. I'm using a topical cream applying morning and before bed. Quite a bit more than estrogen even, I can't imagine going back to not using it.