The only Pentax AF lens I've ever had real AF problems with is the D-FA 100 WR Macro; that one hunts focus like nothing on earth. The DA 35 Macro I found was a lot better, except occasionally when moving between focus extremes.
That being said, I always caution users that it's not for everyone. I bought it for medical photography where I need a wide field of view and ultra-close minimum focal distance at the same time, to properly photograph larger surgical specimens and for autopsy work; actual 1:1 reproduction is in itself not as important to me. I bought it because I was having to stand on chairs or put specimens on the floor to get enough of them into the picture with the 100, and because I didn't want to go to the D-FA 50/2.8 only to find that wasn't wide enough either.
If you...
a) Do not already have a DA autofocus lens in 35mm for your Pentax APS-C body, and...
b) You want macro/ultra close focus capability, and...
c) Can easily afford the price,
...then the DA 35/2.8 is for you. The image quality is superb, but it is not one of those Pentax lenses that has its own special legendary quality. Edge to edge sharpness is the design feature here, but that's what macro lenses were built to do. That being said, I did the single-in challenge with it last year, and
here are the results. Being able to get in so very close makes for shallow depth of field and interesting bokeh opportunities even at very narrow aperture settings!!!
Also: unlike the other two current Pentax digital-era macros, this is definitely NOT a full-frame lens. If the K-1 is in your future or is your only body, you will have to be in crop mode to avoid vignetting, or crop it out in post. I have a K-5 now so this is not an issue for me; those moving from bodies with higher MP counts would have more compromises to make.
Last edited by pathdoc; 03-09-2017 at 08:59 AM.