I always check the following to get exactly the output I required;
InterpolationMode ( DrawImage uses this )
SmoothingMode ( Pens, Brushes etc )
CompositingMode ( over write or blend (( hey Microsoft, can you say Porter Duff )) )
PixelOffsetMode ( watch this one, be sure you understand the implications when stretching images etc to the screen ).
TextRenderingHint.ClearTypeGridFit; ( there are other options but grid fitting is important for good text quality with vector fonts )
-duncan