Hey Zach, are you referring to the carrot accord they share? I'm not a big fan of Iris Silver Mist, I agree with you in that it smells very synthetic - boy we are going to get slaughtered by the BN cognescenti.
For me, it has that humid opacity that is present in so many Lutens fragrances, Gris Clair instantly comes to mind. It's like the feeling of getting out of the shower and not being able to get completely dry, no matter how fluffy and absorbent one's towel is.
If A la Nuit is Death by Jasmine then ISM must be Embalmed by Iris.