Who needs XML?
Been thinking about the "and XML" part of Ajax and wondering why we need XML at all.
For example, 37 Signals recently rolled out its new Backpack web-based PIM application, and I've read a few complaints about how it doesn't work in browsers like Opera and older versions of Safari, presumably (I haven't looked under Backpack's hood personally so I'm going on word of mouth here, careful!) its heavy reliance on XMLHttpRequest for client-server data transfer.
(BTW, that's not meant to be a negative comment on Backpack on my part. Backpack looks VERY cool, and I intend to play with it extensively.)
The obvious reason is, I guess, compatibility with other apps that read XML, but that doesn't seem particularly compelling when 99% of the apps I've seen are built to be run in a JS capable-browser. Why wouldn't you optimize your data format to suit the target environment?
As far as XMLHttpRequest is concerned, as one Opera user stated, "shouldn't it just work without it?"