1. 18% thinner than before.
2. 20% lighter than the 4S.
3. four-inch Retina display. Same width, but taller.
4. 5 rows of apps, up from 4 on prior phones.
5. 4G LTE web-surfing speeds. (HSPA+ is 21Mbps, DC-HSDPA is 42Mbps, and LTE is a max of 100.)
6. Better Wifi, 802.11a/b/g/n, and it’s dual-channel, up to 150Mbps.
7. A6 Chip. That means 2x faster CPU and 2x graphics compared to the A5 chip in the iPhone 4.
8. Better battery life; 8 hours of 3G or LTE talk time or browsing. 10 hours on WiFi browsing.
9. Front-facing camera is now 720p
10. Rear-facing camera is still 1080p, 8-megapixel sensor but better low-light and 40% faster image capture.
11. Better quality audio. Three microphones. Front, bottom, and back for more natural sounding speech*. Carrier dependant.
12. Same price as the 4S. $199 for 16GB. $299 for 32GB, $399 for 64GB.
13. Available on Sprint, AT&T and Verizon, Rogers, Telus, Bell, Fido, Virgin…
14. New connection port “Lightning” smaller, faster, all digital, better quality.
Those are the real goodies, there are some other gimmicky stuff but you can read more about that here.