S/px depends on how long you let it go, my current render is at 40 S/px after 30 minutes.

And I've got the same problem as Laurie and LuckDragon, the view in Luxrender is zoomed out from what I've got in my Poser viewport.
I just zoom in my Poser view by about 20% and then it looks like I want it in Luxrender, but it's annoying, it's a bit of trial and error to get it just right.

Software: OS X 10.8 - Poser Pro 2012 SR2 - Luxrender 1.0RC3 - Pose2Lux
Hardware: iMac - 3.06 GHz Core2Duo - 12 GB RAM - ATI Radeon HD 4670 - 256 MB