Normally, I do not bash equipment. But I just purchased a Metz 58 for use with my K20D, and hoped it would work so well that I would get another one for the other K20D I have (I shoot weddings).
Unfortunately, when I mounted it on the camera, it would not, (no matter what I did) talk to the K20D in P or GREEN modes.
And after further investigation, (which despite significant research was never apparent prior to this), it seems that many of the modes, particularly MANUAL will not work at all.
There were no updates on the Metz Website for the Pentax, so, alas, I have returned it to B&H and am waiting for my 540.
If anyone HAS made it work, please let me know...but for now, I remain disappointed.