Samsung/AT&T indefinitely pulled the update. They've also blocked it for UCKD5 so doing GTG's Ultimate Unbrick won't work anymore either. It's pretty obvious that the Gingerbread build they had released was not stable and had some bugs and issues that needed to be resolved.
The good news is that their team is working on it. Even just recently (two days ago or so), they leaked a new build (UCLB1) which fixed some of the issues on that "official" Gingerbread update that had gotten out before (which was UCKL2, I believe). According to people who flashed UCLB1, it's pretty stable but still has some battery life problems, so I think Samsung/AT&T are testing it further and will either release that or work on another better build for the official update.
You know, the whole fiasco kind of happened because of one AT&T representative who accidentally posted the information on a support forum. Even to this date, Samsung/AT&T have not yet officially announced that the official Gingerbread update has been released. It's still coming. We just don't know when.