Hi. Me and my buddies don’t have any problem with that, but all the girls I know hate U-turns. For the sake of motorized girls (but of course not only!) please consider introducing such a restriction on the Website and in the Application.
I rarely get lost in navi, but I often consciously enter a different route than suggested by navigation because this is my whim (but sometimes a necessity). In that case, a U-turns avoiding would also be useful to me.