There are endeless threads on the 556 on the sigforum. I plan on getting one after some issues are addressed. From what I hear, the trigger is the crowned jewel of this rifle. Standard AR stocks will fit. A lot of people like the CTR stock and they have put folding adapters on them.
The initial ones wer 2-tone, grey on black. Now they are flat black. The first production runs had canted rails which sig is addressing. Most of the later ser#'s don't have the canted rail. Aurora industries is already coming out with original style front sights and replacement push-pins instead of takedown screws.
The people who don't have them complain about them. The people who have bought them love them.
No irons are being included yet.