I have one... pretty much like it except for shots at F1.4 2..10m away.
Most likely its some kind of defect so most of lenses should be fine.
Mine, mounted on k100ds "likes backgrounds".. at the mentioned distances the lens does not back focuses, but if the subject is not large enough to completely cover whole selected focus point (and sometimes even if it is) it focuses to subject right behind it.
If there is nothing behind, the focus is dead on.
Some examples:
Inbox Foto (foto.inbox.lv) (Exif shown at the right side)
Pictures containing IR/OK in title i considered to be focused as i wanted, those with GARAM/NAV are not.
Never had red of this kind of glitch before in internet, so decided some might be interested.
At first i taught it was my incompetence with F1.4, but after more careful testing the results were quite consistent.
In situations other that described, knowing the cons (CA's, distort., corner sharp.) the lens seems to be perfect.
Rich colors, no hunting, sharp in center, good weight balance on k100d, 3d feel in images. Actually i like it so much i dont mind the defect... well.. don't mind alot. But if i had to decide right now, i would rather spend my money on 35/2.
When im shooting with it, it almost seems the same as it was with 50mm helios on my Zenit-E.