It seems to me that the black gaps are bigger. I just did a back of the envelope calculation, using the photos he posted and it looks as though black gaps take up about 30 percent of the space on the first and second iPhone while they take up about 40 percent on the new iPhone 4.
I wonder what the effects of that are. It probably just makes the display a bit dimmer (if one were to use the same backlight).
Though I'm not discounting that it may in fact be dimmer:
Larger gaps alone implies dimmer, but this can be accounted for by having the pixels put out more light. Having larger gaps on a display doesn't mean it's dimmer, as the pixels have likely changed characteristics in the process of shrinking them.
(It’s, by the way, not that the gaps got necessarily bigger, maybe a little, it’s just that they didn’t shrink either and, with more pixels, there are also more gaps.)
The article states that it was harder to focus the optics on the older displays, causing the pictures of them to be blurrier, which could explain the apparently larger inter-pixel gaps in the images of the newer display.
I wonder what the effects of that are. It probably just makes the display a bit dimmer (if one were to use the same backlight).