Apologies all, I know it's a frustrating wait! The initial release of the SDK has been pushed back and you should have it in your hands within the next couple weeks.
Hello everyone! Exciting news! The initial release of the Nintex Workflow 2013 SDK is available!
Dennis Kennedy is Nintex's Programmer/ Writer and he'll be providing more developer focussed content and code across the platforms, each week he'll be updating the SDK with new content and code, and publishing a weekly update. Make sure you follow him so you don't miss a thing!
Read up on his intro post here The Nintex Workflow 2013 SDK is (initially) released! and you can access the SDK here http://help.nintex.com/en-US/sdks/SDK2013/