Thanks. I shoot 95% available light in my studio. This was done with my most-used "set-up." She was seated right next to a window for the main light (camera right, and the biggest catchlight). There is another window on the same wall, further away (next to me basically, to my right. There is another window behind me, on a perpendicular wall, which can add a bit of fill, depending on the time of day. Most of the fill came from a Larson 42" x 72" reflector very close and to her right (camera left). There is a window on the opposite perpendicular wall, behind her and camera left, which acts as kicker/rim-lighting. See photo detail.
I have black covers as well as sheer fabric scrims for each window. In combination with a couple of reflectors (but usually just the one Larson), and changing the angle of my backdrop and shooting position, I can get different lighting looks. It's often been mistaken for softboxes. It's actually better than softboxes, because I can shoot at f/1.4.
The downside is that on very cloudy days, or if I need more DOF, I might be cranking my ISO to 1600 or so. Which has generally not been a problem with my D3, and now with the K-5.