In the meantime, users of Windows 10 Tech Preview build 10041 can already give the new EdgeHTML engine a try by toggling it on via Internet Explorer's experimental web platform features:
[...] Spartan’s rendering engine called EdgeHTML is available in build 10041, and can be tested with Internet Explorer via a toggle in the about:flags page called “Enable experimental Web platform features.”
The IE team said that the March update has several new features and improvements:
Improved ECMAScript 6 compatibility (up to 74% in the Kangax ES6 compatibility test in this preview) Expanded support for DOM L3 XPath Support for WAI-ARIA Landmark Roles Support for CSS Conditional Rules (@Supports) Support for the Web Audio API Support for CSS Gradient Midpoints (aka color hints) Improved FeBlend mode support Unprefixed support for the Fullscreen API
There are also some other features either fully or partially implemented, and they can be activated in the about:flags page in Internet Explorer:
Support for the Touch Events API. (Touch Events are enabled when a touchscreen is present) Support for the HTML5 Date-Related Inputs API. This is off by default. Partial support for CSS Transitions & Animations on SVG elements