This is a simple useful sort of app, and it is very handy. Most importantly it is free. That is the biggest recommendation we can give it. It really doesn't do anything that a number of other don't do.
It lacks one important feature: a 'locate the nearest subway station to me' GPS function. Leaving that out alone is almost criminal. City Transit in the app store does that BTW and comes with the maps as well, though it does cost you. Still, if you've ever been in a NYC neighborhood and couldn't find a subway station, this function is alone is worth the cost.
As the maps are downloaded, it's important to download them ALL before attempting to use it on the subway.
Yes, for those of you who may be wondering, there are times when I've needed a map in the labyrinthian tunnels of the NYC subway station. You'd think maps would be everywhere, but NO!!!!
It's slick, it works and does what it promises, it just doesn't do any thing new, though it is iOS 4 compatible and make nice use of the new graphics.
This isn't even the first 'Official' New york City subway app I've seen and I doubt it will be the last.
The NYC Mate, Free in the app store
Three out of five stars