If you are using C4D for most of your renders like me you probably know that option. I wasn't actually and transparency channels of the materials giving me issues on rendering the scene with AO.
The Evaluate Transparency option is for fixing that. I'm using Interposer Pro plugin to import and control my Poser objects on C4D. For hair especially materials are always have transparency channel. And I had issues with it till I discovered the Evaluate Transparency option. Now everything works fine. Most of you probably know that but I wanted to share anyways.