It's taken quite some time, and I had hoped to have it launched before/during DrupalCon Chicago, but the Omega Documentation has finally launched.
There is a lot more to be added over time, and it will greatly be generated by support requests in the issue queues for Omega, and the contributed subthemes, but for now, there is documentation on creating subthemes, region and zone management, some quick overviews of 960 grid basics, and some FAQ items.
I do plan to also start documenting the Delta module there as well (for now it all links back to my video overview offsite)
If there's anything glaring that's missing in the basics, please post an issue in the Omega issue queue related to documentation or support request, and I'll get it in!
Referenced Link: Omega Documentation