According to Think Secret, Backup 3 will see some major changes from version 2. At first launch, Backup 3 offers users a choice of four pre-set backup plans. The first backs up your Home folder daily to a hard drive, and then monthly to CD or DVD. The second plan backs up personal data and settings to your iDisk on a daily basis. The third option will back up iLife data in your Home folder to CD or DVD weekly, and finally, a fourth option backs up purchased music to CD or DVD monthly. Adding or editing a plan is done via an action menu button. There is also a custom backup option, that allows for greater flexibility than is currently available in version 2.
As for those exclusive widgets, the word is they'll focus on making .Mac features accessible from the Dashboard, like Mail, Backup and others. All I'll say is, after all this time, those had better be some sweet widgets.