enable window 'snap' in 12.04 (window maximation on drag to edge)
Solution 1:
The feature which maximizes the window when dragged to the upper panel is still present, but only in Unity 3D, not in Unity 2D.
Therefore, I would suggest to check if you have the right graphics drivers, because when you don't, Ubuntu will automatically start the Unity-2D session instead of the default, heavy unity.
I did a clean install and tried Unity 3D after installing my nvidia drivers.