Got mine today. Luckily it was powdercoated not anno'd.
I noticed a couple differences from the standard tac8, well at least the one I had awhile back. First aside from the obvious longer barrel ad stiff trigger pull the bolt face is a bit different and lacks the style of bumper/foamie that my tac8 had. Second, the two bolts on the back section are new also.
I relplaced the stiff trigger spring with an identical on that I made out of some springfeed wire I had lying around. Now it feels like my old tac8.