IDNX does provide information that domainers should pay attention to. It quantifies the price trends for various TLDs relative to their own past and to each other. And it shows a strong coupling between domain prices and other measures of economic health. From the vantage point of non-domainers, this means that domains in general can be a robust investment. And, of course, this latest news of reputable financial players embracing IDNX means more exposure, good or bad.
IDNX tends to be criticized for what it's not. And what it's not is most of what people involved with domains care about--namely, an accurate indicator of particular domain values. You can track the price of corn over time on a graph and show that corn has real investment value that correlates with economic health in other respects. But domains aren't cobs of corn. In fact, no 2 domains are the same species. And, while domains in general (or domains that SELL in general) have value that can be tracked, a huge percentage of domain trading is invisible; and most domains have only negligible value and will never sell. The IDNX is like a chart that shows the average price of paintings over time. Yes, it goes up and down. But the real story lies in the difference between a Picasso and a kindergarten finger painting.
Isn't that the problem? Most financial trading -- and most financial indices -- involve some homogeneous species of corn cob. And whatever domains are, they ain't that.