No backwards compatibility
Plays used games
Still uses Blu-Ray discs
Suspend/Sleep Mode to quick resume play similar to PSVita/3DS
The "Share" button for livestreaming your personal content
Release date = Holiday 2013
Here are the official specs.
They did not show what the console would look like, but the controller looks to have some really good improvements with the concave analog sticks Like the 360. I have mixed feelings about the backwards compatibility, but I understand why they dropped it. For one, the system would be ridiculously expensive for them to release if they were to have built in PS3 hardware to run the games, and emulating them is just out of the question. So this could potentially make it much cheaper than the PS3 was when it originally launched. Everything else, including the specs are really impressive.
Single-chip custom processor
CPU: x86-64 AMD 'Jaguar' 8 cores
GPU: 1.84 TFLOPS, AMD next-generation Radeon? based graphics engine
Hard Disk Drive:
Optical Drive (read only):
I/O and communication:
Super-Speed USB (USB 3.0)
Ethernet (10BASE-T, 100BASE-TX, 1000BASE-T)
IEEE 802.11 b/g/n
Bluetooth? 2.1 (EDR)
Digital Output (optical)
But to answer the backwards compatibility problem, they answered it with their recent purchase of GAIKAI. You'll be able to stream and play PS1-3 games instantly. Not to mention that you can remote play those and PS4 games on the Vita (at least they were just showing the PS4 side).
As for the games themselves. If we really are getting stuff like Deep Down which apparently is all in-game, then color me impressed. I wonder how Microsoft can top this.