XHR: on success, on failure, pause an xhr and come back to it later.
yes

Timer/Timeout.
yes

History/state (back button)
yes

Off-line Storage?
no

Interaction with the Desktop applications?
no

Extensibility.
yes

Animation.
yes (script.aculo.us)

Number of Items that can be displayed in the interface without causing memory or computation problems.

Amenable to other technology mashups/ javascript frameworks: Can it be used with other javascript frameworks.
yes (google maps integration: http://www.zkoss.org/smalltalks/gmapsz2/gmapsz2.dsp)

Support for stateless messaging? -scalability

Usability? Bookmarking/Layout font-size changes
yes: font-size changes; bookmarking most likely possible

Browser Portability
yes

Start Time? How big are the javascripts/swf files....
small, all business is server-side

TESTING and Debugging tools. How can you test the GUI interface?
Java debugging through Eclipse

Will the generated HTML be portable and what happens when a new browser comes in?
yes it's portable (on browser it's just xhtml and js)

Remote Process Calls? Different from JSON and XML

Batch XML Http Requests?

Language
XML (XUL & XHTML) & Java/Javascript/Ruby/Groovy