Smart IBL and a Cycles 'shadow catcher' shader

Hi Folks,

There is a teeny thread on www.hdrlabs.com concerning the implementation of Smart IBL sets in Blender I thought might be of interest to some. In particular this comment from tischbein3 caught my attention: http://www.hdrlabs.com/cgi-bin/forum/YaBB.pl?num=1349924037/3#3.

I’m not a programmer, but I am very, very interested in the notion of a ‘shadow catcher’ shader for Cycles, especially with regard to the ease of use of sibl and with speeding and simplifying the management of shadows in Cycles.
Does anyone know if a shader is planned and think that such a ‘loader’ script might be possible to implement at some time in the future? I’m singling out this thread because it suggests that a ‘proper’ shadow catcher is missing in Cycles. tischbein3 does acknowledge that they may be incorrect in their assumptions and I apologise if I have misrepresented their remarks. Would anyone like to comment on the thread?

Thanks for reading and have a great 2013.

Afterthought: apologies, this might be in the wrong place.