I have only a black screen, unless I check "Sharp Overlay" in the settings. Since the plug-in defaults on a preset with this option unchecked, it's quite misleading: I thought it wasn't working at all.
Does it mean I'm missing some underlays?

I use a G3 White Blue 400Mhz with its original ATi Rage 128. I'll try again later with my Radeon 9200, which is supposed to be OpenGL savy.