It seems we are pretty much in agreement on the subject.
It really hoses me off to weed my way to a nice vantage point, lay claymore and a couple of shock grenades, only to have somebody charge through a door or window and mow me down before I can even get off a shot.
As to the camper thing - I usually have to turn off chat, because every time I stop for a couple of seconds, get the lay of the land, and get a kill or two I get called a "bleeping" camper. Seeking cover and trying to get kills without getting killed is common sense. But as the game does no really penalize you for deaths (which I think it should), you are going to have a preponderance of players going 25 and 20 (or so). It makes more sense personally to me to go 15 and 3, get 5 to 10 assists, and take down a few aircraft - and have fun doing it.
It would be nice if they get shot by a sniper on the arms or legs, the victim will drop to the ground in Last Stand position, lose his weapon, be defenseless and he have to crawl a minimum of two meters to get his weapon back. He will be on this position for ten seconds before regeneration triggers.
I know I hate it when I get hit markers. if you hit someone with a bullet they shouldn't be able to move back into cover and wait for you with a shotgun. a hit marker should indicate that you have a kill not that an enemy is eating bullets. I feel like they should either make the bullet damage higher (which is what I recommend) or make it so that their is less cover to move to after you are hit. and seriously I am tired of getting shotgunned or quickscoped after I shoot an enemy in the face.
The problem here is you can't hold your aim long enough to get the kill. Core isn't just about who fired the first shot. It's about who can hold his aim more accurately to get the kill. You can fire first, get a hitmarker, lose your aim and get killed. I killed so many players even though they fired first. I'm a hard target. I strafe, I jump, I dropshot, and I'm pretty accurate. If your accuracy isn't so good, rest assured I will take you down even if you managed to fire first.