Apparently Sony's put a lot of effort into the DualShock 4, although you'd be forgiven for not noticing, given it barely looks any different. However, that light on the front, the speaker and the touchpad really make it revolutionary, at least according to Sony. Here's a quick walkthrough to show you why.
I guess having the controller be able to know that you've swapped places with your mate and switch screens for you is cool, and the speaker on the Wiimote actually makes quite a difference for the Wii, so that's probably a good element to steal from Nintendo.
Anyway, it's not like you're going to have an option if you buy a PS4; you're stuck with the DualShock 4 whether you like it or not. Let's hope it's not a pain in the arse to hold and use with that touchpad on the top. [Sony]