New Version of ember with glimmer engine

I understand that the new version of Ember uses the glimmer engine and that this makes Ember closer to how React.js uses the virtual dom. Is this new version of ember radically different or are the differences something that is more transparent so that when you write your code it is not that much different than how it was before ?

The latter. In theory (as long as you were good about not using private APIs or doing weird stuff), you should be able to upgrade your app from pre-glimmer (<1.12) to post-glimmer (1.13+) without having to make any changes.

If you were doing some manual DOM manipulation or using a jQuery plugin you might find you’ll have a few things to fix, but other than that, our upgrade to Ember 1.13 (Glimmer) was relatively seemless.