I'm new to the software, but just experienced an unfortunate "error in usage".
I had several tasks in the wrong project so I selected the multiple items and (as far as I know) used the "Move To" option.
They didn't get moved, they were set to "Completed" instead!
Therefore my points are.
Maybe a "Are You Sure" warning would be good for actions such as moving, deleting and setting as completed.
Also a "Un-Completed" facility to re-instate wrongly set tasks.
in order to select multiple tasks which you would like to move to a different project, please hold the CTRL key while selecting them and click on the task names (not the check-box). Once you select them, you can use the "Move to project" option from the menu which will appear at the top of the screen.
In order to un-check a task, please click on the "Show completed tasks" link at the bottom of the task list (in each project) and simply click on the checked box to recover them.
Great... Thank you David :-)