I can appreciate why Google would want to add this functionality, but adding a new icon to the system tray (space in there can be quite a precious commodity on a Mac) and providing no obvious way to hide it isn't cool, so I'm disabling for now.

I'd much rather they integrated with the system-wide notifications, or if that's not possible because they want to show "rich" notifications, then at least provide a way to use them without taking up system tray space.