Lots of things behind the scenes such as better network code and support for scenarios and game styles in multiplayer.  Tests have already shown that 6 players have no issues playing.  I'm trying to organize an larger test.  Of course the things that are more  obvious is better "to-hit" effects, which is what is in the screen shots.  When beams hit shields they flare up as blue-white, when area orange-white and the ground, green-white.  When pulses hit something they make larger explosions that are red.  Because of the way things now work, one can now trace a trail with the beams which can be more easily seen in the latter screen shots.  There is going to be a lot of other visual updates in the coming weeks.