Re: Dynamic iris
There are three ways in which an iris can annoy or compromise PQ.
Brightness compression: In a mixed scene (a starfield is always given as an example), the bright stars will be dimmed slightly, in order to give you a lower black level.
Noise (audible): Some iris implementations are noisier than others - often it's a high pitched whine, which can irritate.
Brightness pumping: This is where the iris acts so slowly that you can see the image change brightness during the scene. Pretty annoying, but getting rarer - especially with the newest models.
It's a trade-off, but with a good implementation (like the Sony VW60 for example), most are happy to live with it in order to get much more image depth in dark scenes. I haven't really heard any complaints about the Mitsubishi models either. I can't think off the top of my head how others perform.