I love the DP1x and own a DP1s. My own view is that sharpness is not a problem but the maximum of F4 might be a bit slow for some lightling situations. Speed of focus can be an issue and the file write times are slowish with the camera being inoperatable for several seconds. So I do miss a few opportunities and find the expereince a whole lot less spontanious than I would like. Others may disagree but I think the DP1 needs a more considered approach.
I do use mine for street, but it is a lot more versatile in other areas. I love it for buildings, church interiors, still life and landscapes. I took the attached today in Knaresborough, North Yorkshire, it was a grundgy grey day and just starting to get dark. I used 1/60 at F5.6, ISO 100. I dont say this is a great image, but it is typical of what I get.