I've seen the post that MGI put up over on the "AR Varients" section and have to say that I like that concept. I have to wonder how durable the mounting surfaces are for the lowers and if there is a possibility of it loosening up over time.
I am very intrigued with the AK mag set up though. I've always wanted an SR47 clone and this looks like it might be the closest thing to getting close to one. The AR47 receiver that Special Weapons(?) had just didn't look right and didn't use the regular AR mag catch.
Besides my pipe dream of an SR47 clone, I think the .308 setup is supposed to use a regular AR10 upper. Think of that, a GAP built upper with .308 adaptor for long range precision and a 9mm setup for CQB all on the same receiver and swapped out with the push of a pin.
Either way, this setup is supposed to be significantly cheaper than what Cobb Mfg. came up with and I'm curious to see how it works out.
(Jason, I posted this under your post on "the hide" but thought I'd put my input here too)