I wouldn't use more than one light set to constant. Ever. I do use a lot of point lights if I'm doing an interior and there are lamps, ceiling lights etc. I'll use more than one spot too, like if I'm doing a portrait. But when it comes to lights that essentially equal a sun, I only use one :).

Make sure you use good render settings as that makes all the difference too. You have to take gamma correction into account as well.

Laurie

oops...crosspost ;). hborre knows what's what. Take the advice...hehe.