Nikon 28mm f1.8

I got  my new Nikon 28mm F1.8lens. Initial tests suggest it is a good copy ( a couple of OOF shots seems to be my errors). I am really confused whether to keep this or get another wide angle lens like 20mm f2.8. I already have the  24-85VR as part of my D600 kit and it seems 28mm f1.8 may not be utilized that much. I also have the 50mm F1.8G and 85mm F1.8G for portraits and general shots. I am also hearing a lot of reports of focus issues of 28mm F1.8 lens.

Could anyone please tell me their experience in 28mm F1.8 and comparison with a wide angle lens like 20mm f2.8.

-Madhu