So, the aiSkyDome light shader uses multiple importance sampling and renders better quality than just area lights at the window entrance with directional light.
My settings here on my home machine (Mac Pro 1.1 - Quad Core)
Intel(R) Xeon(R) CPU 5150 @ 2.66GHz
home machine My settings are:
aiSkyDomeLight samples: 6
AA samples: 8
GI (diffuse) samples: 8
Glossy samples: 5
and my diffuse bounces are at 2.
The render took 7.8 hrs.
I am looking into optimizing my settings :]
Diffuse to diffuse path tracing is almost as bad as glossy (specular) to glossy (specular) path tracing.