Quote - I'm wondering if the reason is because PPro 2010 has fixed some IDL bugs. Those bugs were a real headache for me in P8. PPro 2010 IDL is better - not perfect yet like some other apps - but clearly fewer artifacts and inaccuracies. We may see some of these corrections in an SR for P8, and they may slow it down a bit.

Yes, some Indirect Light quality improvements in Poser Pro 2010 can increase render times slightly. I'd say that's CPU cycles well spent.