Using version 1.0.0, I have my language choice set to "System Default", which in my case is US English. The app, however, uses UK idioms. For example, it told me to take the "slip road" and I have no idea what that was. It didn't take me long to figure out that the equivalent US term is "exit ramp", but it would be nice if there were a US English vocabulary.
I thought that was funny initially, but I love the accent and after a couple of ramps it makes perfect sense to me (I speak German, French, and Spanish, as well and that's how I say the phrase, "take the exit ramp and continue straight." I've watched too much BBC to not appreciate the Queen's English. :->) I must admit I did have to change to metric to miles because USA is so stuck in those archaic units and I hate converting in my head.