A couple of points spring to mind:
1) public transit is not a very big advantage. It is useful only in the handful of US cities that have decent public transport. In Paris, one of the great public transport cities in the world, google still doesn't provide public transport information. In 2012. Apple's solution, to rely on 3rd party devs for this has every chance if providing a solution to iPhone users before Google.
2) But even assuming you're one if the lucky few for whom Google provided public transport information, you can still use Google maps from the browser. You can even add an icon in Springboard for it, giving you full access to google itineraries. The only thing that has really been lost is street view.