John,
I have two flip up sights on ARs. I have a Bushmaster V Match 20" with a SWAN sleeve on the flattop. This is very close to the A2 sight including both aperatures. You have to adjust elevation with the front sight though. The only thing I don't like about it, is that it doesn't lock in the "up" position. This has never been a problem, but I'd just like to know that it was held in place somehow. It's very quick to deply, just unhook the catch and it springs into place.
I have the Knights Armament flip up rear sight on a Colt 6920 Law Enforcement Carbine. It has a detent that holds it either up or down. It only has one aperature, but comes with a removable plastic insert that you can use to make the aperature about the same size as the long range A2 aperature or you can remove it and use the aperature like the ghost ring 0-2 aperature on the A2.
I haven't done a lot of shooting with the Swan Sleeve because I have a 4x32 ACOG on it, so I've basically just zeroed it. I have shot a lot of rounds using the Knights flip up sight (through the Aimpoint with the dot off for practice transitioning to irons in case of electronics failure). I prefer to shoot it with the insert in. It must be very close in height to the carry handle sight, because there was almost no elevation adjustment to the front sight when I zeroed it. It was already zeroed for the irons in the carry handle when I put the sight on.
I can't say if the Swan Sleeve is the same way because that rifle never had a carry handle on it.
HTH
Jeff
PS I can bring them both to Phoenix with me next month if you want to try them out.