I have been to the Heard a couple of times in the past few months.
For people who don't know much about Native culture or art AND who think Native artists aren't legitimate, then this museum helps to make the argument that Native Americans are part of contemporary culture.
For me, I found the exhibits interesting, but the sales pitch on each of the labels off-putting. In addition, there was a real focus on the "noble savage at one with nature" that perpetuates the fantasy that Anglos popularized. Art can be valuable because it evokes emotion or mood, regardless of whether it is done by a Native artist or it incorporates nature and culture.
I also found it odd that the building that houses all this "nature-inspired and connected" art has a strong demarcation between inside and outside. It is kind of like a basement.
If you can get a free admission at Phoenix Public Library, it is worth a trip.