I got a chance to use it on a particularly nasty data set my client has that has a lot of fairly deep intervention with LookupRecord and custom services (ie it's cleanup that's way too dynamic for UpdateRecord).
I was able to refactor about 15-18 steps into a single ScriptedTransformRecord that executes a ~ 80 line Groovy script that calls out to a fat jar that has some of our helper methods in it. Suffice it to say, performance went way up and on top of that we now have a simpler code base that is even easier for our CI/CD pipeline to integrate with NiFi. Mike
