Choose the best framework for AJAX development

I started  developing AJAX applications some months ago for playing. Now we're working on some serious web applications and recently I was evaluating a framework to speed up the development process.
I know that in order to make the best decision you should evaluate the scenario, but some of you could give me good advices to solve this dilemma.
I strongly used Rails on Ruby and I was very impressed, therefore I listed alternatives to this framework. I'd appreciate a comment or advice by you :

RICO in Javascript
TrimJunction in JavaScript
Junction in Javascript

SAJAX in Python
DJANGO in Python
Fanery in Python
Subway also in Pyton

Cake in PHP
Symfony in PHP5
Seagull in PHP
Trax in PHP

Rails in Ruby
Nitro in Ruby

Comments

[Supra Shoes]

Web application developers can now reuse existing open source C and C++ client or server-side code on the Flash Platform.

[manny]

http://blog.creonfx.com/javascript/dojo-vs-jquery-vs-mootools-vs-prototype-performance-comparison

Please check the real comparison & best ajax framework.
my best choices and order: mootools, jquery, dojo and prototype.

[Milsonei dos Santos Cardoso]

The address for ExtJS Framework, other ajax framework in javascript is http://extjs.com. The best!