Ok well here is some feedback for the mac demo... firstly thanks so much for porting this, it really is a brilliant game (i have played on windows) you've all really gone above and beyond.
Ok so everything runs well, no random crashes/system meltdowns etc. My system is a 2.33GHz Intel core 2 duo, with 3GB of ram and a Radeon X1600 with 256MB v-ram.
The only issues that i can find are firstly a problem with the shadows. See the image below.
The picture below is the same scene with shadows turned completely off, however you can still see that the rear wall isn't there and neither is the torch/chain/lock/coat on the wall/map on the table so on so forth, some of the textures aren't appearing.
This is all i could find, good job on everything. Also apart from the shadows i had all the effects up at max.
Cheers.
By lowering the shader quality like Secutor said, i can make the various missing elements re-appear, and for the most part the back wall, although it pops in and out.