"Developer feedback also indicated that there wasn't a marked difference between how websites should be developed on Internet Explorer 11 and in its new browser. Microsoft notes that for developers, the new engine in Project Spartan will work with modern Web technologies. In an effort to keep it "evergreen," there will not be new document modes or compatibility views in the future."
Kelly, that's a great thing, compatibility. One of the major issues facing by web developers are browser compatibility, if MS is taking care about it then rest is assured.