I know no one will say it, but yes, IDL is really slow. You can improve the speed a lot by changing settings, but it will always be (a lot) slower the regular render. Why do you think SM did so much effort to improve the render speed of P8 over the previous versions? Without that IDL wouldn't even be an option at all.

Artwork and 3DToons items, create the perfect place for you toon and other figures!

http://www.renderosity.com/mod/bcs/index.php?vendor=23722

Due to the childish TOS changes, I'm not allowed to link to my other products outside of Rendo anymore :(

Food for thought.....
https://www.youtube.com/watch?v=pYZw0dfLmLk