- Import the Tree Creator package from the Standard Assets
- Create a Terrain
- In the Inspector for the Terrain, select the Place Trees tool
- Click the Edit Trees button
- Select Add Tree
- Click on the "small circle" icon next to the Add Tree field in the window that opens
- Notice that the Big Tree prefab has a preview, but the Palm tree doesn't. Something about that Palm tree prefab is broken.

This is a regression compared to Unity 4.3.1 (in which the Palm tree prefab was removed, which is actuall a regression from an older version of Unity where it existed and it worked).