No dual-wield - that was only in one cinematic AGES before release - a very cool trailer, but there's a lot you can't actually do that's shown there.
Also, the ADS delay will probably matter, but so will the long-range stability that it gives - deciding which to use in which situations will be crucial to victory. It already starts getting that way on some of the challenges - when you're close to an enemy, hip-fire is brilliant, but get more than half your gun's range, and you WILL start using ADS if you want to kill efficiently. I first noticed on the "Escort Duty" challenge when I was at the 2 star level - nearby enemies move faster, and it's a little tougher to track them with ironsights or a red-dot, but at a distance, you just cant land your shots consistently without it.
I'm on PS3 too, and can't wait to get online with the game and see how I stand up to other players (probably not the best, but I'll have fun)