I found this article today about UI design issues with Web applications built using form developed with XMLHttpRequest calls.
Usable XMLHttpRequest in Practice | Baekdal.com
It seems that every time we invent a new toolkit for doing UIs, we go through a period of time where everyone uses different conventions and no two apps ever work the same. Then, standards emerge and everyone starts building their apps using roughly the same conventions.
It happened with Windows (remember all the different control libraries?), it happened with HTML, and now it’s going to happen again.
Hopefully we’ll learn from the past.