I find the REST API to be both interesting but also empty. It's needed in core but there isn't as much adoption as I would have thought. The REST API is being used primarily in "proof of concept plugins" and there are very few that I know of that make full and proper use of the API currently. This might just be because of how only the first half was in core but it is interesting that we don't see more adoption of it.

In no way am I saying it should not be included or to be removed it's just a little odd that there is a lot more buzz to get it in core than for those to actually build off of it no?