What is the best Braze feature that is underrated?

I would say Braze Product itself is underratted but very soon its going to become the Mammoth of Martech :)

To be very specific I would say 'Connected Content' at the moment, out of many, Actually it allows marketers to pull real-time, dynamic data from external APIs directly into messages (emails, push notifications, in-app messages, etc.).

Clients often don’t realize they can integrate real-time, external data so seamlessly until they see it in action.

The best point is, Many other platforms require custom engineering to achieve this, whereas Braze makes it straightforward for marketers with a few lines of Liquid.

Once of the more handy / unique features is that once you send a campaign you can send more without creating a duplicate broadcast (With most platforms, once a broadcast is sent you have to create a new one and exclude those who you already sent to).

Example, sent a test to 10,000 by setting a limit, later raise that limit to 110,000 to send another 100,000.

I like the checkbox in the email builder that lets you add whitespace after preview text! 

I personally believe that Braze itself is highly under-rated. Though I am using it mostly for the 'Connected Content purpose, but it is such an helpful platform mate. I love their packages as well. But one thing that I am reading everywhere is the use of edge technology in the platforms algorithms that can automate various processes. I guess, this one's integration will be huge benefit and success for Braze and its users.

This will make our campaigns way more less time taking and automate certain things. I am expecting this very soon. This will also help in more precise target audience for certain campaigns. 

Overall this platform is love and expecting some changes in near future.