I don't get in my car without it.
It's a great map app. It's got a good nav function, but I've found that simply having a scrolling map display with your car in the center is invaluable. What they did that really makes it kick is crowdsourcing the data- users report traffic conditions, accidents, hazards and radar traps. They can even edit the map. All those reports get verified by other users, too: driving along it'll give you an alert to an "object on road ahead" or something, and you can give it a thumbs up or down, either scratching it off everyone's map displays or adding confirmation for everyone.
Here's a shot I took this morning- there's construction going on, but it's a Friday in August and a lot of folks are on vacation so traffic is otherwise pretty light.
They gamify the process. You choose how you appear on your map and to everyone else and the system gives you points for using the app and making reports. Near holidays they'll sprinkle "road goodies" around the map- drive over one and you'll get points. The more points you have, apparently the more weight your reports, etc have.
While waiting in traffic yesterday I checked settings to see where I was in points. With my pathetic commute, I'm #11 in the state. Yay me.