The Sigma 24mm f/1.4 DG HSM Art lens for Nikon mount is now shipping – the above pictures was sent by a reader in Austria who just received the lens from his local Foto Schneider Baden store (thanks Erich).
In the US, Amazon currently is showing that the lens is in stock by third party resellers (fulfilled by Amazon):
The lens is available also on eBay. B&H and Adorama are still on the pre-order stage.
The Sigma 24mm f/1.4 DG HSM Art lens costs $849 (the Nikkor 24mm f/1.4 is priced at $1,929). The Canon version was recently tested at DxOMark and got a good feedback. Additional information on the lens, including MTF charts and detailed specifications, can be found on here.