Should I upgrade my project from Cake 1.2.5 to CakePHP 1.3.0?

My web project (to be launched in a few months) is currently using CakePHP 1.2.5 / PHP 5.1.6 / MySQL 5.0.77.

From a performance point of view, is it a good idea to upgrade to 1.3?

Will it make it easier to later upgrade to the (PHP5-only) CakePHP 2?