As I told Matt Priour, I know for a fact that there are developers at ESRI who get REST. Several are posters to the Geo-Web-REST group. It's clear from the demo that there is resource-oriented thinking going on at ESRI. Consider this map layer home page that you can find through the demo source: SuperTuesdaySample/MapServer/1. There you find metadata and links to subordinate resources such as a query. The HTML representation of the query is a form which doubles as a query description. I am 100 percent in favor of this approach; it's exactly what I've done with Mush. Traverse upward from the layer to the map server resource and you'll also find WSDL and a JSON service description. I'm not against service descriptions at all, but I wonder why not WADL? Or for that matter, why not OWS Capabilities?
This is good stuff. I'm curious to see how the PUT, DELETE, and POST story goes.
Postscript: Looks like James Fee beat me to "view source".