I think this preview render is going to take quite a while to clear up. I wonder if we should somehow prioritise specular/transparent materials and give them a higher S/px limit ?

hmmm, it could also serve as an indicator about how 'tough' the mat is to render :)

Seems to be looking a bit different from first time around.... doesn't have the yellow tint in the middle yet ?!

Looks good with high samples per pixels , I've render up to 11000 samples/pixel ... check it out

http://quentar.avc-cvut.cz/luxrender/matlib/35-Plexiglas_cloudily/plexi-11ksps.png

This material has bumps of 5mm, this seems way to high, it should probably be divided by 10.