XHR: Supports on success and on error handlers but not pausing/resuming an operation.

Timer/Timeout: This feature can apparently be set only on the server side as a hard-coded value; it cannot be set by the client.

History/state (back button): The web browser button can not be utilized, however, similar functionality could be acheived by creating simple graphical widgets that support similar functionality.

Off-line storage: Although it is impossible to store files on the machine it is possible to write cookies using JavaScript for simple data storage.

Browser portability: Since OL uses the Flash plug-in for rendering browser compatibility is dependent on whether or not the Flash plug-in supports that browser.

Testing and debugging: OL supports unit testing; SWFs can be debugged and re-compiled from within the browser for convenience.

Will generated HTML be portable...: No HTML is generated just SWF (compiled Flash file) so depends on compatibility of Flash plug-in with browser.

RPC: Via XML-RPC; only available when using OL server