On stage at today's PlayStation event in NYC, lead system architect on PS4 Mark Cerny revealed some technical specs on the upcoming PlayStation 4. It's built on an x86 CPU, with an enhanced PC GPU and 8 gigabytes of fast onboard GDDR5 memory. Cerny also confirmed there would be a local hard drive.
Cerny also confirmed a secondary chip that handles all downloading, so that downloads can be performed in the background. PS4 titles are also playable as they're being downloaded.