The new Sigma 85mm f/1.4 EX DG HSM is priced @ $899 in the US and is currently available for pre-order.
Here is a brief specs comparison with the current Nikon AF 85mm f/1.4D IF (I will repeat this comparison once the new Nikon AF-S 85mm f/1.4 lens gets released - hopefully by then we will also have sample photos to compare):
Sigma 85mm f/1.4 EX DG HSM lens design:
Nikon AF 85mm f/1.4D IF lens design:
Update: here are the MTF charts for the current (AF) Nikon 85mm f/1.4 (left) and the new Sigma 85mm f/1.4 (right):