Dear Sam,

The problem comes from the use of ImageMagick's "convert" command that was introduced in gs_utilities.cpp in svn rev 4522. I guess suppressing the blurr is a matter of giving better options to convert (like perhaps -density in addition to -geometry), but haven't investigated that yet.
You can revert to a crisp output by the following patch:

###################
Index: src/Plugins/Ghostscript/gs_utilities.cpp
===================================================================
--- src/Plugins/Ghostscript/gs_utilities.cpp    (révision 5232)
+++ src/Plugins/Ghostscript/gs_utilities.cpp    (copie de travail)
@@ -102,14 +102,14 @@

void
gs_to_png (url image, url png, int w, int h) {
-  if (use_converts (image)) {
+/*  if (use_converts (image)) {
    string cmd= "convert ";
    cmd << "-geometry " << as_string (w) << "x" << as_string (h) << "! ";     cmd << sys_concretize (image) << " ";
    cmd << sys_concretize (png);
    system (cmd);
  }
-  else {
+  else {*/
    string cmd= gs_prefix ();
    cmd << "-dQUIET -dNOPAUSE -dBATCH -dSAFER ";
    cmd << "-sDEVICE=png16m -dGraphicsAlphaBits=4 -dEPSCrop ";
@@ -123,7 +123,7 @@
    cmd << "-sOutputFile=" << sys_concretize (png) << " ";
    cmd << sys_concretize (image);
    system (cmd);
-  }
+//  }
}

void
###################

Best,
Philippe