1. Demo ran at 20 FPS
2. Environment detail was compromised (not sure which things, possibly some background effects, particles, and/or textures)
3. The character models were more or less direct copies of the PS3 assets. I think this is clear from the images and videos.

All in all, truly impressive feat for a portable. To achieve those stats based on a simple port of content of a 2008 PS3 game is really exemplary of how powerful the machine is.