Iris Poudre is my favorite iris fragrance, and one of my top perfumes that I have tried. I love the progression, as you have described quite well. I'll add that the supporting florals in the middle are beautiful, not over the top (as I don't particularly like screaming florals ). The drydown is beautiful and long lasting. I love how it goes from quite feminine feeling to rather masculine feeling, and I love the play off of each phase. I do see how it could be considered "dressy", but I wear it all the time and don't save it for special occasions.
Eau Premiere is a work staple, and I agree, a wear anytime fragrance that is just a wonderful blend of pretty/sporty/easy/breezy. It fits them all, and smells great while doing so.