The Attribute module improvements in the library have resulted in better performance of the
val() methods and support for boolean attributes and hooks have been added to allow the two methods to be extended.
Performance has also been improved in event handling, which has in turn improved the performance of jQuery's
data() which allows data to be attached to any DOM element. Other changes see the ":focus" selector working properly across all browsers,
is() methods now all take DOM elements or jQuery objects, relative CSS support ported from the
animate() method and smoother, more synchronised animation.
Some of the innovations may require code changes: case mapping of data attributes now matches the HTML5 spec and, due to the new distinction between properties and attributes, the
attr() methods behave differently. A summary of the changes is available in the release announcement and there is also a list of all API changes.
Work is now starting on jQuery 1.7, which is planned to be released in August.