Hi Eric ..
Some experiences with the designer to use it with eclipse rap demo.
I have downloaded the rap m3 through the update site
To import the rap demo plugin go to import->plugins and fragments->
I have opened the DemoTreeViewPart and it looks good.
If you add some components that will be supported through the rap project it works fine. You can find out which components will be supprt through the components demo.
Some views doesnt work (RWTDemo) but i think it should not be so much work do adapt the designer to wok fine with rap.
To start the rap demo go to Run->Open Run Dialog->Osgi Framework-> Rich AJAX Platform Demo. Under Bundles you should select the
org.eclipse.rap.demo and click the 'Add Required Bundles' Button. Click 'Run' Buttun and it will start on port 80.
To acces the demo go to http://localhost/rap
I think it wil lbe great if youzr designer will work with it ..