From http://beyondunreal.com/

* minimum: 2.8GHz, 512mb Ram,Geforce6
* for high details: 3-4GHz, 1Gb Ram, Nvidia 6800GT/ultra or 7800GT/GTX SLI
* Dual-core Processor use: Multi-Threading is supported and should provide much better performance.
* 64 Bit version available with better textures
* Renderers: Shader-3.0, Fallback-Mode for Shader 2.0 maybe a dx8 renderer.
* HDR: yes
* physics: Novodex-Physik-Engine.
* Ageias PhysX Processor supported.
Holy My gaming PC is toast. I'd like to say "Well, at least I can play it on my work machine, because that thing's a beast" but chances are they'll probably never make a Mac version so that's not the case.