I have an interesting observation....
I am trying to render my old hour glass scene.gallery2.php?g2_itemId=10422
After about 4 hours or so i have this with SPPM, not bad for the power thrown at the scene.
I have one observation in the difference between the two renders. The old bidirectional one has bright reflections of the light sources in the glass and the SPPM version does not. The shapes of the lights are observed, but it seems like it is a passive reflection, like light that is reflecting from the scene back to the light object and back... Is this expected or might I have something set up a little wrong? I made sure my lights had external volumes applied, as well as my camera also. everything in the scene i think is setup in a matter that i think works... and rendering in bidirectional gives me the original behaviour again. Anyone else seen this?