iOS 9.3 is coming in the Spring and will introduce Night Shift as well as a number of other new features.
4th Generation iPad Reviews: Faster, Better Camera, Lightning Port
The changes include a faster A6X processor running at 1.4GHz allowing the device to run twice as fast as its predecessor. The new processor doesn't worsen battery life. Engadget's testing even showed it to be slightly improved. The front facing camera has been upgraded to take HD video, and the only other external change is the replacement of the 30 pin dock connector with the new smaller Lightning connector. CNet sums it up:
The latest iPad adds several tweaks and improvements to secure its position at the top of the tablet heap. It's better all around, but third-gen owners need not apply.The other interesting effect the new iPad has on Apple's product line is that it increases the gap between the iPad 2 and the "new iPad". Apple has chosen to keep the iPad 2 at the $399 starting price point and simply retired the 3rd Generation model, replacing it with the new one. That $100 difference between the two models now represent a larger feature gap than before.
- The Verge