Just a heads up. In pursuit of a Dynamo 1.0 rollout this winter, we are doing a lot of cleanup of the underlying Dynamo code, which has some impact on backwards compatibility. Primarily, we are changing the names for a number of things deep in the code. This does not affect not node names or anything visible on the surface of the application, but rather pieces of the underlying API. The result is that if you are working in the pre-release builds (0.9.1 versions), most file that you save in 0.9.1 will not run in 0.9.0. This is similar to how a Revit 2015 file will not open in Revit 2014, for example. The expected result is that you will get files from 0.9.1 that look like this in 0.9.0 or before:
Keep in mind, 0.9 and 0.8 files will upgrade FORWARD just fine, but 0.9.1 will not go BACKWARD.
For software developers and others coding their own nodes, you can see the list of these changes here: