If you are interested in seeing how XForms can be used as a development environment, I would suggest you check out the new Orbeon XForms Builder:
http://www.orbeon.com/forms/builder
This is a great example of “Eating your own dogfood” where a development tool is used to build other development tools.
Orbeon is a great organization because their forms products run not just inside FireFox using the XForms extension but on any web browser. They do this by running on the web server and translating the specification of the XForms application into HTML and JavaScript. So you can start your development with FireFox and deploy when you need IE support.
We want to contrast the Orbeon approach with the traditional “build yet-another Eclipse extension”. With the Orbeon solution you don’t need to download any client, no custom installers and all your forms can be stored on a central file server, versioned and shared. XForms can be your future IDE.
So my hats of to the guys at Orbeon for this great milestone. Hopefully we will have more XForms-tools-to-build-XForms in the near future…like a metadata registry (hint hint).
Thanks for the kind comments, Dan. You are right on track: Orbeon Form Builder is a zero-install and (at least that's our intent) easy to use piece of software. It is written itself with XForms and it is 100% open source, what more can you ask ;-)
(By the way we are aware of several efforts to write metadata editors based on XForms, including for the MODS format.)
-Erik