I don't think I've ever heard Winslet sing, but what's fantastic about Desiree is that it was written specifically for a non-singer, and Sondheim says that "Send in the Clowns" is supposed to be performed by a non-singer because that's how it was written (hence why he dislikes Betty Buckley's oversung version), hence why so many A-list actresses who would generally not be considered for a musical are being considered for this part. I really can't imagine a better opportunity to have Winslet on Broadway. I still think Kidman would be miscast (doesn't mean she won't be good though), Linney is a hugely missed opportunity, and that from the names I've heard, Emma Thompsom is the most appealing one.
"Some people can thrive and bloom living life in a living room, that's perfect for some people of one hundred and five. But I at least gotta try, when I think of all the sights that I gotta see, all the places I gotta play, all the things that I gotta be at"