Ice, if you are doing an indoor scene with light coming from outside you should create a portal where the light is coming in, that tells lux not to waste processing power on irrelevant areas. Read back through the posts made yesterday.

As you've noticed putting a light inside is going to make rendering faster.

Luxrender is very precise and gives realistic results, that takes time. The good thing though is that it's very easy to add extra network nodes for more rendering power, and once the GPU rendering code is finalised the speed is going to increase by a factor of 10-50x.

Software: OS X 10.8 - Poser Pro 2012 SR2 - Luxrender 1.0RC3 - Pose2Lux
Hardware: iMac - 3.06 GHz Core2Duo - 12 GB RAM - ATI Radeon HD 4670 - 256 MB