More and more of this ‘XML HTTP Request’ stuff is getting coverage as people pick apart Google and other sites using it. The method that people like Basecamp and therefore Ta-da Lists use has been given the name ‘Ajax’ (Asynchronous Javascript & XML). Ajax is basically a method where you update the client using Javascript (which is pretty instant) and update the server simultaneously (using XML HTTP Request) in the background (doesn’t really matter how long it takes). In this way you give the user a nice a responsive user interface, something which the web is not always great at. There’s a good write up of the method here.