WebDesigner is meant to allow a web designer to create a site once and see the site work seamlessly across desktop and mobile platforms.
Working with HTML5 and CSS3, WebDesigner is a WYSIWYG editor that will allow you to work directly with the code. Not only will it create websites, but allow you to create animations like Flash (I personally am ready for that format to die). It also has simple illustration tools, bringing more power to this tool. I don't know if it is a tool for the masses yet, but anything contributing to the death of Dreamweaver can't be bad.