Our experience echoes Globetrotters. And USC definitely had the best package for NMF. That said, my kiddo went to a state university and got no $$ whatsoever from the school and from the College Board. I read that about half of the NMFs get scholarships, too, but we didn't know a single NMF IRL who received one Even though he didn't get a scholarship, though, I do think that NMF was a helpful proxy for ACT/SAT for the test-blind schools, if they were interested in knowing it. (As an aside, it is interesting to me that the current NM award is only $2500. When I got it 8 billion years ago, it was $1500. I think the $1500 was probably relatively more valuable for my costs that were about $10K per year.)
Given that the test is usually given during school hours for most students, I would certainly encourage everyone to try to take it. There isn't anything to lose, and at minimum, it is practice for the SAT.