Don Kuykendall_RIP
RIP :(
In my experience so far the soft focus has only been a problem in low light. In good light I have no problems getting sharp pics. When researching what to buy it was noted in many reviews that the D5100 was weak in low light situations.
I have had great success in low light with the D5100. I have even shot in caves with good results. Don't be afraid to jack up the ISO to get the shutter speed you need. Some noise is better than a blurry or no photo. Take a look at these
http://nikonites.com/project-365-daily-photos/11298-dons-d5100-daily-dabblings-76.html#post201163