So I see that whenever people discuss dynamic iris implementations, they focus on whether or not you can see artifacts (pumping, clipping, etc.). But nobody is talking about whether the DI actually does anything useful to improve the picture. If the DI doesn't actually do anything significant, then of course you're not going to see artifacts. That's been my experience with older Sony and Epson implementations (HW15, VW85, and 8500UB). I never saw the point of it. It didn't hurt or help the picture in any obvious way compared to just closing the iris manually. It seems like a useless feature to me that helps inflate contrast numbers for marketing purposes but does little to help with real world content. Kind of like the crazy dynamic contrast numbers you see on LED LCD TVs.
Maybe I did't test them correctly or used the wrong material. I usually compared a space scene with manually closed iris and using dynamic and never saw any improvement in the black background behind the stars. If anything, the iris was more noticeable in brighter scenes where it made everything brighter by opening more. It made little difference in the dark scenes where I was hoping to see improvement. Toe's comments regarding still seeing gray letter-box bars in dark scenes on the new JVC backs up my limited experience regarding DI. It's nowhere near as useful as the 1.5M:1 contrast numbers imply.