Bug-fixes, some object related optimizations (reducing the total count of objects/resources used from the CPU, making my eventing/link condition checks more efficient) and some balancing changes.
I often forget that it emails everyone each time I update the build. Earlier a friend told me they wanted to playtest so I made sure the build had the most recent things I did.
Depending on when you last played, lots of little things were adjusted to improve the game feel.