Hi there,
 
I recently started using the DrawLineAa method, which is excellent and improves visual appearance of my app while maintaining high performance. I do have one issue with it however. If you clean a WriteableBitmap with Color.Black and call DrawLineAa with Color.White the appearance is odd. Particlularly if you draw a sequence of multiple short lines.
 
I will try to upload a screenshot & demo project later.
Best regards,