I have them. so far I like them. If you want max drop they may not be for you. So far they seem stiff but not unbearable.
Info on spring rates in near impossible to come by, HR would not give up anything. I ended up buying a set from Bmp. I expecting more drop than I got, called BMP and spoke with a tech. He said that they had run lap times with the various springs and that he 50406 produced the best lap times.
Search under my name and should come up with a thread and it will give you the spring rates. I really like them so far but I haven't autox or spent track time with them. FWIW 50406 are sport springs for E30 M3, can't be bad?
I will take some pics if you like.