Originally posted by blende8 AFAIK the Metz can everything the Pentax can, including HSS and wireless. It can even more, it takes the values from the camera in Auto mode, the Pentax doesn't.
Also the Metz has a second reflector.
I read a lot about the AF540 before buying and accepted that in A mode, everything would be manual. Imagine my suprise when I started using it and reading the manual, only to find that in A mode, with the camera body in P or Tv, the flash controls the apeture on the body. This may not be as desireable as the functionality of the Metz, but it is a far cry from being manual.
It actually works quite well in practice. Set the flash to A mode, set the camera body to P or Tv (Tv lets you choose the shutter speed), set the flash A mode apeture and ISO and half press the shutter release. The camera and flash communicate and set the aperture on the body to match the settings on the flash. Even if you ISO settings don't match, the system compensates by adjusting the aperture.
This is explained on page 29 of the manual, granted a little vague.