I have to agree about using this for head and shoulder or face portraits. I use it at 45 mm F/4 for the fastest shutter speeds indoors, usually on a tripod if it is not very bright in the room. My sister's house is lit like a cave. I'll go up to ISO 1600 w/o flash if I have to. Here's an example at 56 mm.I have found this lens really good for portrait type shots, the Bokeh is pleasing.
With the G1 I find that the built-in flash is that good that I can use this lens to take shoulder-up shots of family indoors.
Well this shot is truly candid, shot at Flinders Street Station, Melbourne. It shows good sharpness, bold color, and good resolution at 800 ISO. I'm not afraid to take my G1 camera and 45-200 lens to their extremes.