Gmail tasks got a tweak on March 11, 2009 according to the Tasks Teaks post on the Gmail blog. I don’t use Gmail Tasks on a regular basis but here’s the meat of the new post:

Now you can easily move a task (and all of its sub-tasks) to another list. To do this, simply click on the arrow (or use Shift-Enter) to the right of the task. At the bottom of this screen is a drop-down with all of your task lists. Simply select another list, and leave the screen by clicking “Back to list.”