The new Processing 0133 includes a fix for forcing OpenGL anti-aliasing, making my anti-aliasing hack obsolete . Forced anti-aliasing is implemented via the hint() / unhint() function.

From the release notes:

Added support for full-screen anti-aliasing with OpenGL. This is enabled via the hint() mechanism because it has several tradeoffs and its behavior across video cards varies. Use the options hint(ENABLE_OPENGL_2X_SMOOTH) or hint(ENABLE_OPENGL_4X_SMOOTH) immediately after the size() command to get lovely smooth results. Read the caveats in the documentation for hint().

0133 also contains a bunch of bug fixes, among them a fix for the annoying behavior on Windows where Processing would create a 100×100 pixel window regardless of what was specified with size().