The details were as follows -

 During the game -

"In game you are going to see pretty yellow numbers pop up when you complete objectives, get kills, etc. These are your Experience Points. Experience Points add to your overall ranking during the match. Depending on the matchtype, you will get a different number of points for different actions. And no, you will not be able to carry your rank over into the final game"

 Party System -

Select 'Xbox Live' from the main menu and then choose 'Find Game'. If you want to party up with your friends, select 'Party Invite' from the same menu. You can also jump into matches your friends are playing by selecting their gamertag through the Xbox 360 dashboard, Friend's List and the option 'Join Session in Progress".

Weapons -

Attachments: ACOG Scope, Grenade Launcher, Grip, Red Dot Sight, Silencer
Grenades: Flash, Smoke, Stun
Sniper Rifles: Dragunov SVG, M21, M40A3
Shotguns: W1200
SMG's: Mini-Uzi, MP5, Skorpion
Side-Arms: M9, M1991.45, USP.45
Assault Rifles: AK-47, G3, M4 Carbine, M16A4
LMG's: M60E4, M249 S.A.W., RPD

Classes -

Assault (M16A4/Grenade launcher, M9, Stopping Power, Extreme Conditioning, Frag/Stun Grenades)
Demolitions ( W1200, M9, RPG-7 x2, Sonic Boom, Extreme Conditioning, Frag/Smoke)
Heavy Gunner ( M249 S.A.W., USP.45, Stun x3, Juggernaut, Deep Impact, Frag)
Sniper (M40A3, M9, Flash x3, Stopping Power, Deep Impact, Frag)
Spec Ops(MP5, USP.45, C4 x2, Sonic Boom, Steady Aim, Frag/Flash)

Modes -

Free-for-All ( players: 6-12, Score Limit: 300, Points for Kill:5)
Team Deathmatch ( Players:6-12, Score Limit:750, Points for Kill: 10)
Team Objective ( Players: 6-12, Scorw Limit: 150, Points for Kill:5)
Team Tactical (Players: 4-6, Score Limit: 500, Points for Kill:10

Maps -

Overgrown ( Large overgrown, rural Russian area, Sniper ghillie suits make good cover)
Vacant ( Deserted Russian office, intense corridor firefights)
Crash ( Downed Sea Knight chopper in a desert town, made for team games)

So far these are the only details released but expect more as time goes on.