A few days ago, Microsoft released Windows 10 Mobile build 10080 for participants of the Windows Insider Program. With this new build comes an updated version of Project Spartan (officially known as Microsoft Edge). Microsoft has also updated the Edge changelog, giving us an idea of what's new in build 10080.
According to Microsoft, build 10080 adds the following new improvements to Microsoft Edge: Experimental features interface is available (navigate to about:flags) and Project Spartan is now the default browser on phones. Here are the known issues: Action menu at the bottom of the screen is larger than intended; Issues with full screen content.
For those who didn't know, the Experimental features interface features a hidden settings page that allows you to enable or disable experimental browser features such as a CSS filter property, touch events support, and asm.js. Give it a try by typing about:flags in the Edge browser on your phone, if you have build 10080 installed.