You may not have noticed but I've tweeted about jQuery 1.4 new features. Here is my selection of the best jQuery 1.4 brand-new methods:

#jQuery 1.4 .delay( duration, [ queueName ] ) method seems very useful ! http://api.jquery.com/delay/

#jQuery 1.4 .toArray(); //helper
toArray: function() { return slice.call( this, 0 ); }
#jQuery 1.4 .prevUntil() .nextUntil() .parentsUntil() ROCKS! http://bit.ly/5DDcsv //A new way for traversing the DOM :)

#jQuery 1.4 jQuery.noop() ? I Don't get the point... http://api.jquery.com/jQuery.noop/
noop: function(){}
#jQuery 1.4 .isEmptyObject(obj) //helper
isEmptyObject: function( obj ) { for ( var name in obj ) { return false; } return true; }