At the moment I cannot finish shaders for trees and grass because SpeedTree needs to provide some extra data for each vertex in geometry. This is not possible in Unity now. I contacted Unity support and they are working on rewriting the vertex buffer code to support additional vertex data per mesh instance and also being able to define custom vertex formats. This is going to be a great feature, but it will be done in about 6 months or later. So now I will work on wind manager and culling system and will test it with static geometry. When the vertex buffer code is written by Unity team I will continue rewriting SpeedTree shaders to Unity.

Below are some screenshots of trees with billboarded leaves.