For people like me who live in big cities or travel a lot, the addition of public transit information is a big plus. For basic directions, Google Maps works very well. It's able to find my apartment building in a far-flung neighborhood of the Bronx (though Google still thinks my building is about half a block north of where it actually is). It gives me a couple ways to get there on the subway and bus, along with pretty accurate travel times.
If you have a preference of subway, bus or light rail, you can filter out the other options. The app shows me the correct express bus routes from my office to my home, but fails to mention that it costs $5.50 to ride that bus, rather than the usual $2.25. It also doesn't mention that regular monthly transit passes don't work on those buses.
I also asked the app for light rail options as I live about a five-minute walk from a Metro-North railroad stop. But instead of sending me across town to Grand Central Terminal to catch a 25-minute train ride home, the app offers a convoluted set of instructions that involves taking an Amtrak train to the suburbs and then heading back into the city on another Metro-North train. While technically faster, the directions are far from practical (or cheap).
It's also worth mentioning that unlike what you get with HopStop.com or the public transit agency's website, you can't ask for a handicapped accessible route. That means you can't find out if the subway stop you're traveling to has an elevator (hint: many of them in New York still don't). This can cause big problems for everyone from moms with strollers to the wheelchair bound. But the bigger problem is not having the transit directions at all, as Apple's mapping app is guilty of.