I am running VMware with Ubuntu 14.04. The host operating system is Ubuntu 14.04, and the guest is Windows 8.1 Pro. When I briefly press the super key from within VMware, Ubuntu displays the keyboard shortcut overlay, and it does not go away. How do I stop this from happening?
Pressing the Super key invokes the Unity Dash.
Pressing and holding the Super key invokes the keyboard shortcut overlay.
I suspect you are doing the later, based on your description.
Nevertheless, you could change the key used to invoke the Unity Dash using Unity Tweak Tool. This way, VMware will get your key-press signal immediately, when you press Super.
Install Unity Tweak Tool
sudo apt-get install unity-tweak-tool
Launch Unity Tewak Tool.
Show the launcher.
Select a different key (or key-combination) to invoke the launcher.