I've been doing quite a bit of AR research lately. Mainly because of that 5.56 round. The AR-10, 7.62 platform would be nicer, but they are harder to find. I picked up (held) that Sig a couple weeks ago at a gun shop when I was looking for its pistol version (
P556 Pistol), but I didn't realize that the rifle was chambered in 7.62 instead of the 5.56 that the pistol is chambered in. I really thought the Sig 556 meant 5.56 for both models . . . if the rifle was called the 762, it would make more sense.
From the talk and reviews I've read on them vs the AR, people were complaining about the weight and incompatibility with AR parts, so I am still shopping because I am almost thinking it could be nice to have two uppers to run on the same lower - one chambered in 5.56, and one in 7.62 for the ability to scavenge more types of rounds if need be. I'm still pretty new to tactical style rifles though, so I'll be doing plenty of shopping for a while.