I have a "sky lite" (4ft by 8 ft.) in the dining room that I really enjoy using. The light constantly seems to be in a state of change. Much like David, I like to leave a "set up" up for a bit to see the changes in lighting as it occurs. Somehow or why, my wife is not greatly enamored with set ups that stay around for more than a day or so.
I am able to control to a degree the light coming in from the North glass patio doors with a panneled curtain. Available fairly soft light is my favorite, but I do enjoy playing with harsh (bright sunlight) and the games it plays bouncing and reflecting off different surfaces. I will use "gobo's", reflector cards, screens, mirrors, black velvet to subtract light etc. to get
the effect the way I want it. I also enjoy using "found light" I suppose it is related or kin to "Available" but I call it found, and do nothing to change it.
No reflectors or tinkering, kind of like Ansel's ''Moonrise over Hernandez" I just try to get it on film the same way it is presented to me.
I can and do use artificial light on ocassion, but somehow that feels like I am cheating my self of the challenge of doing "still life" with natural light sources. Love cloudy days!