Marc Gobeil has just finished completing some Draw2D Enhancements for GEF 3.5 M4. Marc completed adding anti-alias support and filling out the missing SWT line attributes in the Draw2D graphics implementation. Draw2D now supports fractional line widths, line offsets, line cap and line mitres.
Marc also provided a pretty cool Draw2d example that demonstrates the various line and drawing options available in Draw2d. Check out a couple of screenshots below: