Welp, guess I'm getting a PS4.
So my thoughts are pretty brief, it looks very nice. The new features seems like fun novelties, but not neccessarily something I'll personally use very much. Being able to stream games from the PS4 to the Vita, Wii U style, makes the Vita a way more attractive handheld. The games they were showing off looked pretty good. Knack looks like a tech demo, but potentially a fun tech demo.
InFamous: Second Son is going to be the thing which sells me on the platform. It's going to be weird to see them try to continue from either of the VERY DEFINITIVE endings for InFamous 2, but that series storyline has always been so hilariously nonsensical that it doesn't really matter. Time travellers will fix it all, or something. I find it interesting that they're going in a police-state, dystopia direction with the new one. It was already kind of that, but it was mostly implied that it was that (through the news segments), rather than made explicit. I eagerly await the new InFamous, since both those games have been hugely fun, and hilariously nonsensical.
I find it weird that Johnathon Blow's The Witness is now a PS4 exclusive, since Braid was the first real breakaway hit of Summer of XBLA. I can't comment on Drive Club because I don't like racing games at all. Killzone: Shadow Fall looks potentially cool, I like the Berlin-Wall-Esque divide between the two cities, but I have never played a Killzone game. Watchdogs and Destiny both still look cool.
The tech seems solid enough to me, but I'm far from an expert. I really, really hope the rumors about it blocking used game sales are false.
Looks pretty cool, I'm sure I'll get one at some point.