Re: "The SD1 is a camera that will work magic in studio or landscape photography"
I had an SD-14 which could produce astounding images at low ISOs and in bright light, but the noise issue and general mechanical unreliability with an overheating sensor and poor sealing made it an immensely frustrating camera to use. When it was good, it was better than any APS-C camera of the period, but it couldn't rival a full frame camera.
The biggest issue for anyone who thinks about switching to Sigma is that you are pretty much stuck with using Sigma hardware and software. Many stores won't carry lenses with the Sigma mount and the range is not huge, and as for the software - if you ever thought Adobe produced the worst software on Earth you haven't been unlucky enough to Sigma Photo Pro. Slow, buggy and incompatible with just about everything.