I prefer a standard 60w incandescent bulb about 5 feet away. It's based on the level of lighting I usually see at museums (not that my stuff will be in any museums any time soon...). Never judge wet prints. Dry them and live with them for a while.
Like Brian, I have struggled with this. It's not the level of illumination I have a problem with, but the print color. I try to stay away from looking at my prints under daylight for that reason (and I print at night anyway) but sometimes I can't help myself and days later I'll keep walking around the house to see what the print looks like under different kinds of light, mixed daylight/incandescent etc.
I'll throw another wrench in - the mat board color in relation to the print color. Walk around with a mounted print and try incandecent vs daylight vs halogen spots vs mixed lighting. Yikes.
To Mainecoonmaniac: Dry down is not an issue unless you make final printing decisions based on wet prints. Dry your test prints either in a microwave or with a hairdryer or whatever. Eliminate the variable.