faster processor (1.2GHz quad core, previously 900MHz Quad core for the Pi2)
WiFi and Bluetooth on board, so no need to use a USB port and WiFi adapter.
Greater stated power requirement, 2.5A vs 1.2A
Be interesting to see if the Pi3 power requirements are actually any greater than a Pi2 with the WiFi adapter plugged in, the Pi2 really needs a good power supply to work well with lots of peripherals attached