The ray-traced preview is quite close to the final render now, although of course at lower detail and higher noise (depending on settings and the time you allow it to refine). We'll have some settings for turning off things like "true lighting/GI" to allow you to get faster response in exchange for lower accuracy. Sometimes (like in animation previewing) you just want super-fast response, and sometimes accuracy is more important, so those options will be useful. But if you want the preview to look really close to the final render it can.
- Oshyan