Yes we all heard about the ranking and leader boards and what not. But here is a article from USA today which sheds light on a few missed things about the mode
There's so much happening with Call of Duty: Modern Warfare 3 that Game Hunters has already chimed in with the latest on the Modern Warfare 3 story and the Call of Duty phenomenon.

Another great aspect of Call of Duty: Modern Warfare 2 that's getting upgrades in MW3 is Spec Ops, the single-player or cooperative combat aspect of the game.

In Modern Warfare 3, Spec Ops gains its own progressive ranking system, online matchmaking system and leaderboards. There's also a new survival mode that plays out on the multiplayer maps; Modern Warfare 2's Spec Ops missions took place on single-player maps (as will the new game's traditional Spec Ops mode).

"All that stuff really fleshes out Spec Ops and adds in a lot that we know our fans are going to love, some of the most addictive aspects of Multiplayer," says Infinity Ward creative strategist Robert Bowling.

I teamed up with Infinity Ward executive producer Mark Rubin for a couple tries at Spec Ops' new Survival mode on a map currently called Dome, a derelict Cold War-era desert radar command bunker.

As we dispatched ever-increasing waves of enemies, I discarded my pistol for a shotgun. Rubin passed me some in-game currency and I bought and installed a turret to keep the evildoers at bay, while I watched for attack dogs.

After a few waves, the attack dogs became suicide bomber dogs that exploded a few seconds after you shot them. The next wave brought the kamikaze soldiers who exploded similarly.

"You definitely have to change up your strategy as the enemy changes up," Bowling said afterward. "Obviously how you fight the kamakazi dudes is different from how you fight the normal dudes and how you fight a dog is different from a dude and how you fight juggernauts, they are not only big and armored, so they will just brute force come at you. But they each have their own way of being taken out effectively."

Yes, there are juggernauts returning from the previous games; there will be several different types of them, too. But back in the game, I took heed from Rubin on how to counterattack choppers raining fire from overhead. The game has an unlimited number of waves. "We got up to wave 8 which is really a good wave for a first time player," Rubin pronounces afterwards.

"You were certainly very animated," said Michael Condrey of MW3 co-development studio Sledgehammer Games. "That's a good sign that you were having fun."

In truth, Spec Ops was already a favorite mode of mine that I used in advance of the few times I ventured into the online MW2 multiplayer matches. The developers hope that even more players use the mode to perhaps graduate to multiplayer.

"We have all been challenged. There's such hard-core players out there in the online community and you hear all the stories about (youngsters) swearing and ruining the experience," Condrey says. "With Spec Ops, you can really get in there and hone your skills in a more confined environment. I think it's a little more of an easy entry. I don't have as much time as I did when I was 20 to be honing my twitch skills, but this certainly gives me a venue to experiment."

Adds Rubin, "we added Spec Ops as the third game mode," Rubin says. "That is really stepped up this time. It is really a stronger leg of the tripod."