See and Buy this product on Amazon.com store (affiliate):
DPReview8.1 It's expensive and pretty [...], the X1D is a serious piece of photographic equipment. [...] Its image quality is also up with the best we've ever tested and it provides the tools to help you access that quality. [...] Its advantage starts to evaporate in any low light situation, because of the smaller maximum apertures of its lenses. The X1D isn't a fast camera, either in terms of operation or autofocus. [...] Rather limited battery life.