I've had numerous people ask me about high ISO, but I think they're missing the point. You purchase this camera to capture superb images in a slow methodical manner and are justly rewarded. It's not a point and shoot, although it may look like one - and there the problem lies.
As you indicated when you first got yours, the AF is actually not that bad, and as you also indicate its an ISO 100 camera only as far as I'm concerned.
"but if only Sigma had made the camera a thing of beauty" Indeed. That its not, and I'm having real trouble equating the two. I'm still trying to work out how to start writing about it, which is proving more difficult than usual. I usually have an instant response to cameras but this one has got me somewhat bewildered. The Michael Reichmann review at Luminous Landscape pretty much sums up most of what I think about it - http://www.luminous-landscape.com/reviews/cameras/sigma_dp2m_review.shtml - however I want to not just repeat that.
I'm never usually at a loss for words!! but I am struggling with this.