My biggest complaint is that it is not grammatically correct. I'm no expert, but "It's ambulance," is just plain wrong. Even though it was free, I'll be deleting it. If they fix that, it's okay.
The other major issue is that the music is very obnoxious for a children's app, with no option for turning it off. That made me drop my rating from a 2 to a 1. Sorry guys!
It has 3 vehicles. Even for a free app, that's not many. (Some of the train apps have as many as ten with real photos or videos.)
It would also be nice if when you clicked on the vehicle, it zoomed in, so kids can see what to click (lights, wipers, horns, sirens).