Sporting a (Octa) 8-core processor, 5-inch display with a resolution of 1920x1080 (at 441ppi mind you, topping the retina display, though the HTC one already beat that with 469ppi), 4G LTE, 802.11ac Wi-Fi, Bluetooth 4.0, MHL 2.0, an IR port (for acting as a TV remote), the usual GPS, accelerometer, gyroscope, compass, proximity and light sensor combo, a barometer, a temperature and humidity sensor (I'm not making this up), 2GB of LP DDR3 RAM, a 13MP camera on the back, a 2MP camera on the front, up to 64GB of internal storage along with a microSD slot for up to 64GB of more storage space.

And it's up to date running Android 4.2.2 along with sporting some Samsung specific features like the ability to use both cameras at once, create animated GIFs, use the phone without touching it and I presume multi-window since the S3 now has it.