Shadow Data partition

Hey guy's

Wondering if anyone has any experience with the Shadow Data Partition for Replicated shards.

I am indexing about 10k Messages a second in my 9 data node Cluster and looking to grow volume, and this new feature sounds like something that would be really worthwhile checking out.

I am on Elastic 2.3 right now, probably will upgrade this month to 2.4 just to try to keep up with releases.

Any comments on behavior, pitfalls, or just conversation would be of interest to me.