Multisampling can improve visuals of effects like Desktop Cube or Magic Lamp.

From effects' perspective, all what they would need to do is to set PAINT_SCREEN_MULTISAMPLE(or something like that) flag in prePaintScreen, e.g.

void SomeEffect::prePaintScreen(ScreenPrePaintData &data, int time)
{
    // Bookkeeping stuff, etc.

    if (m_multisampling) {
        data.mask |= PAINT_SCREEN_MULTISAMPLE;
    }

    effects->prePaintScreen(data, time);
}

Current issues:

• GLRenderTarget is not flexible enough, one can't use render buffers. Extending the API would be probably painful.