The Retina iPad at 2048x1536, with a battery nearly twice the size to drive it. Replaced after seven months.
Released March 16, 2012 · Discontinued October 23, 2012 · From $499 (16 GB, Wi-Fi)

The third iPad brought the Retina display, doubling resolution in both directions to 2048x1536, which is more pixels than a 1080p television and was the highest-resolution screen on any consumer device at the time. Driving that many pixels cost something. The A5X needed a quad-core graphics unit, the battery grew to 11,560 mAh to hold the ten-hour figure, and the tablet gained back some of the thickness and weight the iPad 2 had shed. It also ran noticeably warm, enough that the complaints had a name within days. Apple replaced it after seven months with the fourth generation, the shortest life of any iPad, which annoyed a great many people who had bought one in March.
The Retina display was the whole of the story, and reviewers said as much about the rest.
It's only with the display that Apple made a truly big step forward here over the iPad 2, and for many that's enough to make an upgrade worthwhile.
The new iPad doesn't do anything substantially better or particularly different than the iPad 2, offering the same rich world of content as before.