As most readers, familiar with my comments about the inadequacies of continuous light sources know, I prefer studio flash whenever possible. The modeling lights of the studio flash provide "what you see is what you get" photography. WYSIWYG is one of the reasons that many photographers want to lean towards continuous lighting sources. There have been many posts regarding the adequacy of using compact flourscent bulb units for portrait photography.
I have a softbox which uses four 150 watt equivalent compact flurescent light bulbs for illumination. The soft box is 24" x 24" with a silver reflective lining and a diffuser in front. I bought it for lighting in my home when shooting with my dedicated video camera. I use this light in combination with an on-camera 160 LED unit. The lighting the combination produces for my video is quite nice.
However after I shot video of these two puppies playing, I decided to see what stills would look like if I used the soft box as the main light. Here is a shot with the softbox five feet from the puppies. This provided me with a 1/30 second @ f/4 exposure using ISO 320.
Actually, ISO 320 is higher than I prefer to go when I shoot portraits. I normally shoot at ISO 160. However, I needed ISO 320 to get a decent hand-holdable exposure. The IS allowed me to shoot at 1/30 second and get a decently sharp image, except when the puppy moved his head. You can see the results.
IMO, 1/30 second is not fast enough to shoot still images of subjects which may move - even move slightly. Although, the softbox "seems" like it pumps out a lot of light, it really doesn't. I usually shoot portraits with my studio flash using ISO 160 at 1/60 second @ f/8. Since the only light in the room will be from my studio flash (modeling light and then the flash exposure) 1/60 second will freeze any movement. An f/8 aperture will allow me a decent DOF but, since I use around 135-200mm for my portrait shots, the background is still selectively OOF.