High-res, high-DPI not really all that new
The assertion that a display of this resolution has never been done before is misleading. Consider the IBM T221 (http://www.amazon.com/IBM-T221-22-2-3840x2400-Monitor/dp/B00006HS5R). It's a 22" display with a resolution of 3840x2400, for a DPI of 204. This isn't quite as high as what they want for the iPad 3, but it's very fine and with even more pixels. And it was produced in volume. (I could be wrong, but I think IDTech made the panel.)
The assertion that a display of this resolution has never been done before is misleading. Consider the IBM T221 (http://www.amazon.com/IBM-T221-22-2-3840x2400-Monitor/dp/B00006HS5R). It's a 22" display with a resolution of 3840x2400, for a DPI of 204. This isn't quite as high as what they want for the iPad 3, but it's very fine and with even more pixels. And it was produced in volume. (I could be wrong, but I think IDTech made the panel.)
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