So you might be a little confused about this, if you're a small business owner or manage smaller ad accounts you likely haven't used Power Editor much (or at all). I've managed Facebook accounts with a high amount of spend, and still have only used Power Editor for specific purposes (duplicating several ads across multiple ad sets, making changes that need to happen simultaneously). Power Editor is more useful as your campaigns become larger, and more complex; but now all of us that primarily use Ad Manager are going to be looking at some big changes.
It remains to be seen how big of an impact these changes will have, but it seems that the most useful facets of Power Editor are being imported into Ad Manager and this will lend greater flexibility to campaign creation. For those interested in using Instagram Story Ads, this should make things a little simpler. They will no longer have to be silo-ed in their own campaign!
In the wake of AdWords rolling out a completely new interface (that I'm still getting used to), there is a part of me that would like to see Ad Manager just stay the same; but this change is happening and we will likely get some good out of it. Facebook is clearly gearing up for a big year with the rolling out of branded content in ad manager (just create an ad, choose existing post, and branded content may be one of your choices if partners or influencers are tagging you in posts of their own), this change to the platform, advanced measurement (cross device platform that is new) and process revisions around how ad posts are created. Get ready people! If you need any help in Facebook, just contact me here