When using draw.polygon with gfxdraw.aatrigon to emulate filled, anti-aliased triangles, downward-facing edges are jagged where upward-facing edges are correctly smoothed. I believe this is caused by an asymmetry between upwards and downwards-facing edges in draw.polygon, rather than a defect in aatrigon. Shrinking the solid triangle only partially solves this issue. Unfortunately, this is just one example of the difficulties faced when trying to draw filled, anti-aliased shapes with pygame.
Please see the attached program for an example of the problem.