I wish I knew where to look for it, but as I understand it, today's sensors can't be optimized for both ends of the spectrum - low and high ISO. Since "the marketplace" places the emphasis on high ISO low ISO suffers a bit. And that is why some sensors start at 200 ISO.
Anyone know more about this?
I'm with you PDH - I'd rather have a clean low ISO with strong dynamic range. Lately, I've been shooting a lot with tripod and I don't need the high ISOs. Also, I don't mind grain/noise at higher ISOs! But still, maybe someday we can have it both ways!