New iPad has great high resolution display. Some applications is already use it, but some still not updated and render in low resolution. New iPad has 1GB RAM and A5X processor. iPad 2 has A5 and 512MB RAM. CPU speed actually not changed. Only graphics is faster. Device heating up a little and weight noticeable more (+60 g). More time to charge needed.
Some test speed results could be found on
http://www.glbenchmark.com/result.jsp
http://browse.geekbench.ca/geekbench2
CPU benchmark:
135 iPhone
135 iPhone 3G
285 iPhone 3GS
390 iPhone 4
625 iPhone 4S
460 iPad
750 iPad 2
750 iPad 3
1000 = Mac G5 (2003)
GPU (Trigonometric test: balanced)
1.5 fps iPhone 3GS
1.4 fps iPhone 4
4.7 fps iPhone 4S
1.3 fps iPad
5.5 fps iPad 2
9.9 fps iPad 3 (1024×768)
2.2 fps iPad 3 (2048×1576)
Except 5MP rear camera, only real improvement is retina display, GPU, memory and battery is simply adjusted to the new screen requirements.
For USA it also LTE/4G
