Mootools, Scriptaculous, Prototype, YUI or JQuery?

[eluser]Edemilson Lima[/eluser]
This list of web sites using jQuery is pretty impressive:

http://docs.jquery.com/Sites_Using_jQuery

I was looking at the code of jQuery and comparing it to other frameworks, and I must agree: jQuery is more easy to learn. It doesn't have some nice built-in utilities like YUI (HTML Editor or Suggest box, for example), but there are a lot of good plug-ins developed by others that covers all needs.