The video on the Apple site shows a button and states:
"To Do Items: Forget manually adding a new item to your To Do list every time an email hits your inbox. Use To Dos by simply highlighting text in an email, then clicking the To Do button to create a To Do from a message. Include a due date, set an alarm, or assign priorities. Every To Do includes a link to the original email or note, and To Do automatically appear in iCal, complete with any changes you make. And since To Dos are stored with your email (when using an IMAP mail service like MobileMe), you can access them from Mail on any Mac."
Yet it is not showing in Mail for me.