The first Cypripedium to flower for me was the primary hybrid Aki Pastel. Truth be told I find these plants underwhelming. I can appreciate them because of their large flowers and vigor and persistence in the garden, but the color pattern does not, in the clones that I grow, tend towards the pure white color of other "pastel" variants in other crosses. Two clones flowered in early May. I like the spreading nature of the lateral petals in the first clone.
In contrast here is Cypripedium Michael Pastel flowering for the first time. This is an excellent plant! So far it has the purest white flowers of any "Pastel" variants to flower. Its amazing to me that a hybrid with such difficult to grow parents is so easy to grow.
Cypripedium Inge has taken several years to establish but has finally flowered for the first time. I quite like this hybrid and hope it continues to develop and add more stems.
A plant that has been in my collection for a long time is Cypripedium Maria. I started about 10 years ago with some seedlings from Germany, and only a couple of clones are left, but the plants are indestructible and increase in size and flower every year. The flowers have the sweet fragrance of the Cypripedium parviflorum parent.
Cypripedium Sam Saulys is a cross of Cypripedium Gisela x Cypripedium xandrewsii from Gardens at Post Hill. So far this plant has great vigor, large flowers, and good coloration.
Last but not least is my favorite of them all -- Cypripedium kentuckiense. These are a couple of several year old seedlings from Spangle Creek Labs. These are two of my favorite clones.