That caliber 889 has some weakness and definitely not as robust as ETA 2892 or Rolex 3135, but i thought it still be fine for daily wear. One thing that in the earlier model of Ingenieur SL, IWC used ETA 2892 , until about 2001 to 2003 they changed to JLC 889, which is inside my watch. So i think IWC still considered that caliber 889 was fine for their tool watch.