Here are the basic points:
-Splitscreen Online is now confirmed for the PS3 after already being confirmed for the 360.
-Players can ether be guests or can sign in with their own Gamertag*. Guests can rank up, but their stats will not be saved.
-The new Custom Games editor for Private Matches, where you can tweak almost every aspect, from time and score but also what Perks and/or weapons can or can't be used. Custom Games can be saved and put of for file sharing so other players can download that game and play it.
-Matchmaking can be set to Global or Regional.
-New, built in Friends list interface allows for easy viewing of recent games, stats and files up for Download. it will also allow for easy joining of a friends match that is in progress.
-Emblems are one of the only things that don't reset when you Prestige.