How do you like NiFi? I work at Alteryx (we have a closed source visual data integration tool targeted at business analysts and data scientists), but was actually investigating NiFi quite heavily before I joined my current company. It didn't appear to me to have much adoption, but that was over a year ago. It certainly looked extremely compelling as a tool targeted at advanced users.
So I would agree that its not intended to be a tool that you could use like yahoo pipes. To the extent that it requires programming, I guess I would agree it requires an advanced user.
Putting that aside, I would say the Nifi is easy to work with, performant with large datasets, and I personally love the notifications I get when tasks get screwed up, etc. I would not suggest using this to expose data flow to your user as its UI is not really geared towards folks who are programming averse (to a certain extent).
