If your using it as signal generator to display an alternative to cross hairs or "wings" for true ILS data fair enough the terrain data cant be trusted unless someone calibrates the ILS using the same info.
If your using it in GPS mode to generate a persudo VORTAC approach then flying it down the boxes with no error flagging or secondary cross check of GPS error you need your head examining.
Although quite whats so hard about getting two needles to form a cross I really don't know.