AA/ACP would of course be faster and easier to use. The drawback to the Mazda system is how quickly the maps become outdated.
That said, navigating home actually takes 4 inputs if you've assigned a Home address. Press the NAV button, choose "Navigate Home", press to confirm destination, then press again to start. The odd part is that saving Home as a destination in your Favorites doesn't provide any benefit. Still takes 4 inputs to start navigation from Favorites. Ideally, I would just press the * button, then choose Home as a destination. Instead, I also have to confirm the destination, then actually start the navigation.
I'll have to look again. I don't see why it should take more than two. Press Nav. Press Navigate Home. Or better, press the voice button and say "Navigate Home".