The "Beyond REST" moniker is a little propaganda-ish. REST has its place and is a great architectural paradigm. Apart from that, the slideshow was pretty useful and informative. For me, it couldn't have come at a better time -- it pointed out a couple things about XMPP integration that no one had really clearly explained before. (For me, it helped clarify the distinction between XMPP itself and IM, and how one would build an app to leverage XMPP servers.)
Yeah, a better title would have been "beyond RSS."
Or more generically "beyond polling." Polling is a great and simple solution for a range of problems (and why it's often one of the first tools programmers reach for), but as they point out PubSub often scales much better.
I still wonder if we don't need both options, subscriptions and polling. Because otherwise, it would also be very cheap to subscribe to LOTS of things without really being interested (like those people on Twitter who follow 10000 users), which would also result in pushing unnecessary data around. Not sure if this would be handled by "presence", but even so - I want my client to receive all updates, even if it is down sometimes (no messages should be missed).
Great feedback. You absolutely need both RESTful APIs, and these XMPP data services we talked about. We definitely aren't suggesting getting rid of all your current APIs and moving everything to XMPP, e.g. we talked about reusing your URI described resources as your XMPP pubsub node descriptors so you can build hybrid apps.