Popovers could be easily much more versatile, easier to use and more impressive:
- no need for a button, just show them by script. Could be used for splash screens, dialogues and any kind of messages or picture previews, help and much more.
- optionally no triangle at any side. This way a popover would look like a dialogue or inscreen window -> dialogues made easy: Webdirect compatible, no need for a dialogue editor etc. Plus popovers could slide in like sheets in Mac OS X
- optional window element gadgets like close buttons for popovers.
- and as eye candy: Different animations bringing up the popover: sliding in from any side, getting larger, coming down and bouncing on the window bottom. In flat design interfaces animations are the new eye candy and attract the users.