Loved the demo, but;
1: it seems to have less performance than Overture. Levels are alot more complex, but still annoying.
2: In the demo level, I through the box (the one you put in the box) and it went through the floor, forcing me to restart the level. I recommend adding a layer beneath the ground, checking to see if any objects enter it (if it does, than respawn them far above)
3: Can't think of anything else
So, here are the pictures.
Don't know processor
ATI x1550
1.5 gigs of ram
No back ground processes; I was a bit lazy and didn't fine tune the Penumbra settings, so I had slightly choppy framerate.
My screen resolution inside Penumbra was not fit for my computer; however this never caused any problems with Overture.
All of these glitches turned on/off depending on the angle and sources of light.