1) It wasn't the weapons it was lag. I know because I did not have the issue you are describing. I found it a little too easy to kill people with a sniper rifle (M40A5) at distance. That has been corrected.
2) Beta was incomplete. The game should now allow full control of key mapping so yes.
3) Weapon customization will be the same. You get 3 attachments for your primary weapon. I don't remember the exact layout, but I did have a suppressed P-90 with an extended clip and laser at some point. I believe they were Sight/Accessory/Modification. So you can have a laser with a ACOG and a fore grip, but you can't have extended mag and foregrip.
4) Cover is a smart thing to use, but there is no cover system. You get to cover by putting something between you and bullets. But there is not cover mode or shit like that.
5) Depends on what you want to play. I have no intention of picking one cause I want both.
1) I noticed it in single player against bots in BF1942-BF2142 (zero lag). You found it "a little too easy" in BF3 beta?
2) Key mappings aren't the issue--it's the fact the ceiling is too low for jets to strafe and the helicopters don't default to a hover state. In helicopters, I always ended up getting in a drunken-like sway that never ends (correcting, overcorrecting, correcting, overcorrecting, etc.). It wasn't fun like in games such as GTA3-4, Just Cause, or Red Faction: Armageddon. I always have to focus on staying in the air instead of blowing shit up. I'm not going to buy a joystick/controller just for that.
3) Awesome!
4) Great!
5) Same. A friend of mine wants BF3 more than I do. Deep down, I really don't want it no matter how good it is but...I feel almost obligated to get it. It sucks.
There definitely seems to be a lot more ballistic / bullet drop characteristics in bf3.
That was the appeal of the Delta Force series but, how the bullet would behave was very predictable. It made the game more fun rather than being a nuisance like the older BF titles managed to do.
Speaking on stupid ballistics, Brothers in Arms was the worst for it. I'd unload clip after clip after clip and it was sheer luck that a bullet would manage to hit. I was so, so, SO happy when I get a scoped rifle and didn't have to put up with that BS anymore. Needless to say, I never bothered to play the third game in the series. I had enough of it after beating the second game on the hardest difficulty.