Lots of good feedback here, but I feel like the question could have been worded better the PR only allows Node.js to be built on ChakraCore if somebody wishes.
Everybody seems to want to make this a Miscorsoft thing but ChakraCore is MIT licensed. If Microsoft abandons/takes it in an offensive direction then one of two things will happen. It will be abandoned or forked.
Either way everybody will just keep downloading the official Node built on V8. The core node team has made it clear that keeping the shim working for future node versions will be the Chakra teams job so this doesn't slow down development either.
For this reason I think it is a great idea. I also really hope somebody creates a shim that works for Spidermonkey as well. That way there are many choices for both preformance and politics of what companys people like.
I would also like to note that the V8 team has been very hard for the Node.js core to work with. They put the needs of Chrome above all the time. Given Microsoft actually has a business reason to want server side and IoT JavaScript I have no idea how working with them could be worse then Google