I'm not gonna go over all the things they announced as it has been done lots of times by people more eloquent than me, but I did want to mention a couple of things that made me excited as a developer.
The system will be based on PC architecture.
This will probably mean that it will be very similar to writing an openGL game in C and C++ to PC hardware, probably with some kind of Linux architecture in between. This is of course great as it is way more simple and close to standard PC development than the proprietary Cell architecture the PlayStation 3 used.
More downloadable games with different payment options.
It seems Sony has smelled the roses with Apple and Android markets and the upcoming Ouya console. Free games and games with in-app purchases will be something they support. It sounds like we will have a much lower bar to entry, giving a lot more developers a chance to play around with this platform.
Hopefully all this will mean that independent game developers will soon have more great options for making and distributing games.