Excerpt: My experience with flashes is as follows : Pentax AF280T, Vivitar 285HV, Pentax AF500FTZ, Yongnuo 460, Yongnuo 560, Sigma 530 ST DG and now the Pentax AF-540FGZ. I've tried a bit of everything.
Pros: Powerful, offers just about every control possible
Excerpt: This is my workhorse flash for DSLR use. I've become addicted to the wireless mode. Put this on a shelf somewhere, aimed at the ceiling, and use the camera's built-in flash for control and fill, and you get professional-looking results anywhere. I've used this setup for everything from children at play to indoor architectural shots.
Pros: Nice power, wireless features, good manual modes
Cons: Does not have the professional build of older flashes
Excerpt: I've had this flash for about 2 years and in all other respects, apart from the flimsy battery door, it has served me well. I particularly like how easy it is to change settings & to use wireless mode, etc.
Pros: Easy access to settings, wireless mode, HSS etc
Excerpt: A good powerfull flash, which matches the Pentax bodies brilliantly. For easy photography it works very good: TTL techniques makes sure you get a well-lit image. Tilt and swivel head makes it possible to to use the reflective walls/ceiling and more depth in the image. That was the reason to buy a 540 (and not 360 instead, although I did not need the enourmous power of the 540).
Excerpt: I agree with the above review. I have seen two used and advertised with broken slide-in diffusers. I purchased mine used, mint complete with case, box and papers for $300. Amazon is currently showing them retailing over $400. I do not use it a lot with my K20D, but it has been very satisfactory so far.