Some of the more interesting perks about the PS3 version are (Whether these features are on the XBOX 360 or PC version is still not known to me but this is what I have found so far So I am NOT claiming these features to be PS3 exclusive. I am posting this because I thought since these facts are confirmed for the PS3 version they should be posted)
1. Split Screen online gameplay:
You can now play split screen AND ONLINE, you can either choose an existing profile on the PS3 such as your brothers profile or you can make a temporary guest account for someone who just wants to play the one time, the guest account loses all stats once it's been signed out of.
2. Customized game modes:
Now you can customize your private games EVEN MORE, you can choose what weapons to make available, what perks to include / exclude and typical stuff like game mode, time limit etc too, such as a knife only game where all weapons are disabled and everyone has to play using knives ONLY.
You can even share your gameplay on File Share so that other people can download them or view them, kind of like replays for Super Street Fighter 4.
3. In game friend stat tracker:
Are you curious which friends are playing the game and what level they are? there is this neat feature which lets you see all your friends game records, their file shares and everything. It's also pretty neat if your the competitive type and are on a race against time with your friend(s) to see who reaches the max level first.
4. Regional Match-Making & Private Parties:
Prior to Black Ops release date there were rumors that the match making would be strictly regional but now ITS OPTIONAL you can choose global and regional match making so that you are not limited to just playing with players from a specific part of the world.
Party privacy has been improved further the host can now decide who enters, leaves and even decide whether he wants to keep his lobby open or invite only. With an enhanced system you can now join games in progress.
5. Emblems DO NOT vanish when you prestige
Are you proud of your Emblem or simply likes the way it looks? and then you decide to prestige and you see it vanish? WELL NOT ANYMORE, while everything else WILL still get reset in prestige such as perks, weapons, XP etc your emblem will stay the same say that you can shine in all your glory.
Once again I would like to stress that THESE facts are confirmed for the PS3 version so far and there hasn't been any news whether the PC or XBOX 360 version will support these features or not.
Source: PlayStation Blog (US)