This image was rendered with the "VirtuaLight" global illumination renderer. It seems not to support caustics from planar area lights... Rendering time was about 20 minutes on a 233 MHz Pentium II.
I am very curious what other global illumination renderers are doing with this test case. I would be very pleased if someone could render it with Mental Ray, Brazil, etc. and send me the results. Visit the Download Section and get the scene file in various formats for importing it into your favourite renderer.
Another comparison with this test scene can be found at www.buildart.com/render_comparison.htm.
Currently it shows renderings of Truespace, Bryce, Art*lantis and Archicad with AV-Works.