Samsung Galaxy S 4 vs. Galaxy S III: what's changed?

Well apart from the camera and the processor not a lot has changed. No doubt the software will have seen a fair few enhancements also. Interesting that they have brought back an IR LED, I haven't seen those since the old Nokia days. Must be a lack of faith in NFC or something....

At first I thought the screen size might be off putting and cause headaches for the Galaxy note but it appears they've fitted this into an almost identical sized unit to the SIII.  As it's not got wider, you shouldn't need to adapt if your used to Swiftkey / Swype which is a big plus.

From engadget :

	Galaxy S 4	Galaxy S III
OS	Android 4.2.2 (Jelly Bean)	Android 4.1 (Jelly Bean)
Processor	1.6GHz Octa-core Exynos processor / 1.9GHz Quad-core Qualcomm processor (varies by market)	Samsung Exynos 4 / Qualcomm Snapdragon S4 MSM8960 (varies by market)
Memory	2GB	1GB / 2GB (Variants)
Display	5 inch Full HD Super AMOLED	4.8-inch Super AMOLED
Resolution	1,920 x 1,080	1,280 x 720
Glass	Gorilla Glass 3	Gorilla Glass 2
Pixel Density	441 ppi	306 ppi
Storage	16 / 32 / 64 GB User memory + microSD slot (up to 64GB)	16GB / 32GB
Primary Camera	13-megapixel BSI AF	8-megapixel BSI AF
Secondary Camera	2-megapixel BSI	1.9-megapixel BSI AF
Cellular	GSM/EDGE/UMTS/DC-HSPA+/LTE Cat 3 (bands vary by market)	GSM/EDGE/UMTS/HSPA+/LTE (bands vary by market)
WiFi	WiFi 802.11 a/ac/b/g/n, HT80	802.11 a/b/g/n, HT40
Bluetooth	4.0 LE	4.0 LE
Navigation	GPS / GLONASS	GPS / GLONASS
Connectivity	NFC / MHL 2.0 / IR LED	NFC / MHL
SIM	Micro-SIM	Micro-SIM
Battery	2,600mAh	2,100mAh
Weight	130g	133g
Dimensions	136.6 x 69.8 x 7.9mm	136.6 x 70.6 x 8.6mm
Colors	Black Mist / White Frost	Pebble Blue / Marble White
Details accurate at launch. Variants relates to differences in regional handsets.

http://www.engadget.com/2013/03/14/samsung-galaxy-s-4-whats-changed/