air

How easy and quick is it to build a simple project.

It is pretty straight forward to setup the sdk and the application. But I did not find well explained documentation of the SDK, I could refer only the API reference. The API reference is fairly well written, so should not be much of a problem.

How will the JavaScript communicate with the Native Backend.

Adobe AIR lets you create HTML-JS based AIR applications, so using Flash/FLEX is not mandatory. Note: HTML-based AIR applications can only be developed for the desktop and the extendedDesktop profiles. The mobile profile is not supported.

How are JS objects in JavaScript sent to the backend, and how easy is it to read them? Do they need to be encoded purely into JSON as an intermediary?

As the application is compiled and run by the AIR JS engine, all the JS objects remain as is.

Can the JS make async HTTP requests to any other web server without cross domain restrictions?

Yep and you can also load files asynchronously.

Is there a way to have synchronous calls to the backend without using AJAX all the time to talk to the backend.

No Ajax required

Does the system need to be recompiled when backend changes?

No

Does system need to be recompiled when frontend code (JS/CSS/HTML) changes?

No, just save your file and run the app executable, no compilation anywhere.

If no recompile necessary is there a way to reload a specific view without restarting the app.

As far as I know, I had to restart the app to reflect the changes, they were not picked up on the fly.

Is there a webkit/firefox type inspector built in to debug the javascript.

Yes, it is called AIR Introspector. You need to include this js file. More here -> http://goo.gl/SXttXk

Is it possible to debug the backend code easily.

No backend code.

What platforms will this support?

All desktop platforms. Mobile is not supported.

Can you cross compile? meaning can you build an app for OSX while on Linux, etc...

It works on all platforms, you do not need to compile.

How easy is it to distribute apps built with this platform. Will this give a standard system like DMG, binary tarball (linux) and installer (windows) which users are used to.

Very straightforward, you can package your application as a .air file More here -> http://goo.gl/iHoFp

If you need to update the application is there a straight forward path to do so.

You just have to update the copied sdk files.

Does this provide cross platform library to access lower level hardware like the sound card, etc (not using HTML5 audio) in case someone needs to build a more complex system.

Yes it does provide access to Audio, Video, Native Window, Net, System and other low level hardware.

Will this work on chromebooks?

Any platform with AIR runtime