Overall an outstanding unit, very hard to fault and easily fitted. some brilliant features, eg: it can be locked for string changing etc, has lots of adjustments FR's only dream about, If I had a gripe, it would be the tremolo arm, pretty soon after I began using it,(maybe 6/7 times) it ruined the thread,(in the unit not the arm) and needed to be tapped again,minor niggle if you have the gear handy, other than that, Im converted. You would simply never use a FR again.
The Kahler is a unique design that achieves the pitch stability of a locking system, with a far greater vibration transfer to the body than a knife edge pivot. To my ears sustain and resonance are better than with other locking vibratos.