Some very knowledgable people are debating WSDL first. I think reading these types of threads where you get not only people's opinions of pros and cons, but the why's start getting answered too.

It starts with Craig Andera's post about protecting himself (and the world) from poorly written WSDLs by implementing iXMLSerializable.

This post woke Tim Ewald out of his blog slumber who, as a big contract first proponent,thinks that Craig's proposal is overkill.

Craig responded.

Aaron Skonnard got in on the conversation.

Christian Weyer did too (in Craig's comments) since he's got THE tool for doing contract first web services.

All in all, very educational thread, whichever side of the fence  you are on. Me ... I'm just, as always, on the fence.