In a disappointing turn, Apple has removed transit directions from their Maps application (which was powered by Google Maps) with the latest version of their mobile operating system, iOS 6.
No longer can you access COTA directions via Maps on your iPhone, iPad, or iPod Touch (if you choose to upgrade).
There are free apps, though, that will admirably replace that functionality. HopStop is one example - it has transit directions for dozens of cities (including Columbus) and is fast and easy to use. It has a website and also an iPhone app that give very detailed directions for every route you may need in town.
The Hopstop iPhone app also has great functionality for forcing the app to work with stops other than the one it recommends, gives multiple times for departures of buses, and gives the full name of the bus routes in question. It contains all the functionality of the transit options from the Maps app and more! It can even give you the estimated cost of a taxi for the route in question.