I have both the KISS and YPRO shorts. The KISS chamois is okay, but the YPRO is much better for longer rides. I always swore by them, esp, since Castelli's sizes can accommodate smaller pelvises (er, pelvi?).

HOWEVER... ever since I purchased a pair of Specialized BG Pro womens shorts, I won't wear anything else. Specialized makes three levels of shorts and their Pro is the top of the line. Their inseam is a bit shorter than most, and they're a bit pricey ($150) but my girly bits think they're worth every penny. Plus, they come in XS.

P.S. Specialized's jersey line is not nearly so special. I still prefer Castelli on top.