How good does Gps-Navigation on the bangle.js 2 work?

I've added the global.GB function to handle my type in the lcars app js:

global.GB = (_GB => e => {
  switch (e.t) {
    case "bangleOSM":
      if(e.turnIn || e.turnNow){
        turnAlert(e);
      } else if (e.turnType) {
        turn = e;
        drawNavInfo(turn);
      } else {
        turn = null;
        drawPosition0();
      }
      break;
    default:
      // pass on other events
      if (_GB) setTimeout(_GB, 0, e);
  }
})(global.GB);