Here are some of those reports, by different new K-5 users:-
1. Overexposure with 3 Different External Flashguns Except at ISO 100:
http://www.pentaxforums.com/forums/pentax-dslr-discussion/119630-my-2-days-old-k5-faulty.html
2. Out-Focusing and Inconsistency AF Issues with DA*55 and DA*50-135 SDM Lenses:
http://www.pentaxforums.com/forums/pentax-dslr-discussion/119597-new-k-5-i-need-help-focus-issues.html
3. Un-Cooperative Auto ISO and Overexposure with Flash:
http://www.pentaxforums.com/forums/pentax-dslr-discussion/119808-k-5-flash.html
4. Stuck Shutter Release Button Overnight!
http://www.dchome.net/viewthread.php?tid=944050&extra=page%3D1
(Traditional Chinese, machine-translated English Here.)
5. Auto Rotation Not Working for Photos! (But it works for displaying status info in-camera!)
http://www.dchome.net/viewthread.php?tid=944866&extra=page%3D1
(Traditional Chinese, machine-translated English Here.)
http://www.dchome.net/viewthread.php?tid=944866&page=1#pid11114265
(Yet Another new K-5 user reported that his unit suffered from the same problem.)
6. ISO 70 Bug(?):
http://www.dchome.net/redirect.php?goto=findpost&pid=11115061&ptid=944866
(No further information is provided, though.)
7. Obvious Physically Short-sighted (by observing the lens' distance scale):-
http://www.dchome.net/viewthread.php?tid=945579&extra=page%3D1
(Traditional Chinese, machine-translated English Here.)
Well, this is just a great news for macro photographers, or it should be treated as a Bonus! ;-D