We treat Android like Linux, and so it’s a base OS layer

I don't think that's a fair comparison. Android does not just provide the kernel, it provides the audio, video (multimedia), graphics, networking, I/O, and application runtime stacks. It has all the user land libraries there already. All Amazon is doing is replacing the UI layer and some of the default applications.

It's more akin to Ubuntu taking Debian and adding Unity and the Ubuntu services and whatnot.

I may be wrong here, but I feel like Amazon is not giving Android enough credit in it's Kindle Fire line. For instance, on the Fire HD page, there's only one mention of Android hidden in the apps section. It's not even listed under the specs.

Actually, I think there's a little more time than that. The Kindle Fire page has a countdown clock that says there's almost 12 hours to go, so you've got until 10:00 PM EST.