I've only shot at box speed and developed in DD-X. The combination gives a really fine grain for 1600, in my eyes, and has a very nice tonality. The true speed may be closer to 1200, but I never felt the need to shoot it any way but box.
An example, http://www.flickr.com/photos/segedi/...57625198332802
Bit hard to tell at that size, but I think it speaks to the sharpness you can get.