It is a big deal. You can no longer just right click apps to run them, you have to take a trip to a subpanel of system settings, after clicking though two different dialogs that are designed to scare you into thinking something is wrong (one mentions malware by name).

For normal users this might as well be impossible.

Remember, your average user needs a shortcut to /Applications inside the .dmg image otherwise they won’t know where to drag the app to to install it.