Bryan Jones' lengthy blog post boils down to one simple conclusion: "So, if a normal human eye can discriminate two points separated by 1 arcminute/cycle at a distance of a foot, we should be able to discriminate two points 89 micrometers apart which would work out to about 287 pixels per inch. Since the iPhone 4G display is comfortably higher than that measure at 326 pixels per inch, I'd find Apple's claims stand up to what the human eye can perceive."
Mind you, not all experts agree. DisplayMate president Raymond Soneira has dismissed the iPhone 4's Retina Display as false marketing and hyperbole. Jones explains in detail why Soneira's analysis isn't correct, saying "While Dr. Soneira was partially correct with respect to the retina, Apple’s Retina Display adequately represents the resolution at which images fall upon our retina." We don't hold a degree in human vision, but if there's a doctor in the house, feel free to share your thoughts in the comments.
In somewhat related news, analysts believe Apple may have sold as many as 1.5 million iPhone 4 handsets in the first day of sales. An estimated three quarters of those people owned a previous model of the iPhone.