I have one, and it's fine, I just use my FA31 more often because it's the FA31!
Have you read all the forum member reviews?
KiwiJono updated his from 2013 to take into account the K-1:
"UPDATE - FF:
Now I have spent time with this lens on the K-1, my opinion of the FA35 and has only improved further! Its a great match with the K-1, light, small, sharp, fully usable wide open, and bokeh sees a surprising improvement (possibly due to closer focusing distance for same field of view). Also stopped down to f16 I'm seeing nice star flares (like DA15) - see f16 example below!
Its my most used lens on the K-1 and I have increased my ratings to reflect the performance on the K-1. Tempted to give it a 10 overall but build is not quite there.
Samples FF:
At f2:
Old cash register | Jonathan Wilson | Flickr
At f2:
Ford V8 | Jonathan Wilson | Flickr
At f5.6:
Curio Bay beach surf | Jonathan Wilson | Flickr
At f16:
Motorway fun | Not ideal conditions last night as there was ? | Flickr
APS-C:
Its a great lens and is particularly useful on a crop DSLR (field of view on crop is close to 50mm full frame).
Definitely had to spend some time fine tuning the auto focus (on the K-5) because it was out quite a bit. Once I dialed it in though it is returningg very sharp photos.
Its pretty sharp in the centre of the frame at f2 (a bit soft in the corners) and I find it very usable. Even better the contrast wide open is surprisingly good. Sweet spot seems to be f5.6 where it is very sharp across the frame. f4 is nearly as good as f5.6.
I have noticed a little CA at times but its pretty minimal.
The supplied hood is good and can be fitted in reverse over the lens body when not in used - protecting the lens.
So far I am happy with bokeh and have not seen anything I would call ugly but then when I am looking for bokeh I shoot mostly wide open. The lens can focus relatively closely too - which helps.
I have scored this lens 9. On one hand this seems a bit high given that there are better lenses around (costing more) on the other its a great all round lens and good value. The DA 35 f2.4 may well be the value king but I find f2 useful.
The more I use this lens, the more I'm liking it. I'm seeing a lot of good results even at f2. For example take a look at the second f2 image taken in bright contrasty light - there is a little CA (have not attempted to remove) on right side of the dragon head but otherwise its impressive with good contrast. Very comfortable with the 9 rating now and f2 really is handy.
Samples APS-C:
At f2:
Of the rails | Shot with a Pentax FA35 f2. Enjoying this len? | Jonathan Wilson | Flickr
At f2:
dragon glasses | Christchurch Santas Christmas Parade 2013 | Jonathan Wilson | Flickr
At f2:
Larnach Griffin | Jonathan Wilson | Flickr
At f4:
Sunset over the house | Jonathan Wilson | Flickr
At f5.6:
Anantha | Christchurch Santa Parade 2013 | Jonathan Wilson | Flickr
Read more at: https://www.pentaxforums.com/lensreviews/SMC-Pentax-FA-35mm-F2-Lens.html#ixzz5eEWDaj7S"
Get some popcorn for this guy finding it the best of the selection on his Sony A7: