Jeff Atwood definitely votes  for strict snapping to the pixel grid. My opinion is different. I do respect the pixel grid, but only in the Y-direction. In the X direction the sub-pixel positioning must be allowed. In this case we can reasonably sacrifice some sharpness (very gently!), but obtain freedom.
from the AGG Project (Anti-Grain Geometry) [an Open Source, free of charge graphic library, written in industrially standard C++. ]