Not that this makes it better for anyone or is an excuse, but here is an explaination in my opinion of whats going on.
1. Nokia said it would roll out GDR2/Amber for all Lumia devices by Sept, 30th, and technically they have, some were rolled out directly to devices and some to the Carrier for distribution. So technically they have met their deadline for all devices.
2. The biggest reason AT&T is holding back is not for ANY TESTING purposes. The reason other US carriers have rolled the update is that they do not have a more current model WP8 Nokia device that is in competition with an older Lumia device. AT&T is the only carrier with the latest model Lumia, from a business stand point, if rolling out the update means that as few a 1 person doesnt use an upgrade to go from a 920 to a 1020 and extend their contract, they are going to hold off on the update if even roll it out at all. Unfortunately we live in a world where instant profit for share holders takes the cake over practices that value building long term customer relationships.
3. I am not on their side, its still terrible user support IMO and I hate it as much as everyone else does.
Just think of this, if VZW released a 1028 after the 928, you think the 928 would get GDR2/Amber............NO WAY, VZW is far worse than AT&T as far as software support for non current release devices.
P.S. for all those "Im out when my contract is up" people. A word of advice from someone who has had service from al 4 major US carriers as well as worked for T-Mobile, Sprint and AT&T, all them suck, its about picking the one that sucks the least. They are all out to make money and will always place that before device software support. There are FAR to many "Dumb" customers that are fine with what they get and dont understand having support as far as software updates like we do here on the WP forums.