Started having problems with the AF slowing to a crawl and it is still in my 30-day return for refund period so even though I bought it at a better price I decided to send it back.
My decision was based on the reading I did while trying to see what is up with the lens. I found SDM is, on it's best day, kinda fragile. Again, Pentax surprises me in that this sort of technology has been around over a decade yet here is a premium line of lenses with a fussy AF system and only a one-year warranty...then I find there have been a lot of issues with the SDM failures.
So, I am putting any further SDM, specifically DA* lenses on hold. I cannot afford to be stuck in a year with lenses that have either lost their resale value and/or have failed simply because I used them anywhere but resting on a silk covered feather pillow.
(hey hyperbole is fun...hehehe)
BTW, you know how frustrating it is to search on just SDM? Some days I wanna slap the crap out of the original developers of vB...hehehe...I realize it saves on indexes to not allow less than 4-characters but well, for this stuff it sorta matters...but Google is our friend and does an OK job finding the posts & threads...just me whining is all...
I LOVED the 50-135 and it is a big concern to basically have it die of crib death in under 30-days...all with never doing more than sitting in it's bag on a shelf and some basic use for product shots.
BTW, i am one who does not see the rational for wanting to be able to select the screw drive over SDM...I bought the lens with the more modern AF system being a significant feature and see no reason to accept anything less than perfection. FF/BF issues I can live with but mechanical failure and the degree of it is just not worth the risk considering the short warranty and cost. I'll probably grab a cheaper WR DA lens for an all-weather lens for now. If it croaks well, no huger investment compared to the DA* lineup.