V8 is a great scripting engine on its own. I've been using it to allow some runtime scripting in my C++ App, which also makes things a lot easier to debug. It's always nice to see improvements to it, especially since I'm considering to do some core features, such as the rendering pipeline, through js bindings instead of C++. Would make it easier to quickly prototype, test and benchmark different OpenGL calls, shaders, etc.

JS has also become nice to work with since ES6. Incredibly easy to set up a working environment, amazing debugging capabilities, you can just change a few lines and instantly get to see your result by pressing F5, etc. The only really big downside is that static typing is missing, but right now I'd rather not have static typing than go through the additional hoops of setting up transpiler builds. I'd probably switch to typescript if it was natively supported by browsers and V8, but JS is just fine till then.