This is my favorite bra.  I own several in dark colors and they are NOT matronly.  Very comfortable and NO issues with clasp coming undone.  I tried on countless bras before finding this one and will buy them until they are discontinued!
Cup is not an irregular shape.  This is not a push-up bra.  Its more like what I consider a no-show t-shirt bra. Mine are a 38D- perhaps in the larger sizes the cup/clasp become an issue.