Pretty much a PS4 that has been boosted and overclocked with a whole 1GB of RAM more.
I can't see it being as spectacular as most of my PS4 friends think, especially after this from Mark Cerny.
“We want something for people who have 4K TVs, and something for people who have 1080p TVs. Really, there are so many choices: For 4K TVs, yes we'd like them to have super high-resolution. But if [devs] also wanted to have lower-resolution graphics and higher frame rate, that would be very nice too. And so we encourage that. And for HDTVs, if they want to do framerate that's great, if they want to do graphics that's great.”
I think everyone is expecting high resolutions AND FPS.