Not sure what to think about the PS4. The reveal in no way amazed me like the jump from PS2 to PS3 did , or Xbox to Xbox 360 did. Of course, that is to be expected, but I really think we're starting to hit that point where a new console does not mean "Welcome to the Next Level". I look at footage from the last PS3 conference and find it just as great looking as the PS4 conference. Sure PS4 has more detail and light and little details like that, but we all know that sort of stuff is only achieved with a large budget and we will probably only see the difference between a PS3 and a PS4 game when it comes to some AAA titles.
A lot of the "wow" moments are starting to be more of the unseen bits, like faster loading times and minimal startup times. Stuff like social integration (the share button) is less of a next gen innovation and more of a perk that comes with new hardware. It's not as though stuff we see with Wii U and PS4 when it comes to social elements aren't possible on the PS3 or 360. They just weren't built in from the start. So a new console means a new canvas for additional ideas, but I don't get the feeling that these new ideas were added because it was never possible before. More because, like I said, the hardware is new so they have the opportunity to start from scratch and add new things.
Lack of backwards compatibility is sadly a deal breaker for me. If it is promised, soon, that a bulk of the PS3 library will be playable on the PS4 via digital downloads, I'll be happy. But as of now, as a 360 owner there are still loads of PS3 games I've yet to experience and there is no way I'm plunking down more cash for a PS4 when I can get a PS3 for less and access to all the games I've wanted to try.
I guess thats another niggle, the fact that PS4 does a lot of what PS3 does. Shelf space is not something I have much of, and a PS3 and PS4 side by side is a bit too much for me personally. Two devices connected to the same social network with access to different games but using the same account (I assume they will keep PSN ids) but then there are different digital titles between the two, then the fact that both are blu-ray players and media centers. Would one shift everything but PS3 games to the PS4, and keep their PS3 hooked up just for their PS3 library? I guess so.
Anyway, that's my personal negatives. But overall PS4 crushes the Wii U. PS3 to PS4 may not be a big step up for me personally (I know hardware wise it is, but I'm not feeling it yet), however Wii U to PS4? It's like Wii compared to PS3 all over again.*
*I refuse to go further back and note Dreamcast compared to PS2 because I love SEGA too much.