Some developers had a taste of Chakra in an early Windows SDK back during Windows 8.1 development. Back then, the API’s allowed for hosting of Chakra outside of the browser in a very limited way. The limited API’s focused on server-side scenarios and only had been only accessed by Microsoft products like Outlook.com and Azure DocumentDB.
The Windows team go into length about the upsides and positives of this new change on their blog. From memory utilization to start up and execution efficiency, it looks like having access to the Chakra engine and the improved JSRT API’s is a net positive for future development on Windows.