Blizzard design chief Rob Pardo explained the features of the new Battle.net that would ship with StarCraft II at a BlizzCon panel today. The Xbox Live-style service features unified friends lists, chat, achievements and identities across Blizzard games, "cloud" play so you can access your StarCraft II save from any computer, and a league and tournament matchmaking system for players of all skill levels.
Players will log in to StarCraft II as if it were an MMO although it will be possible to play offline, you'll have to do so as a guest.
You'll be able to access your friends list at any point, whether playing camapaign or multiplayer, and it will be unified across all Blizzard games, starting with World of Warcraft. "Toasts" will notify you of when friends log in and score achievements, and you'll be able to send out speech-bubble "shouts" to invite friends to play with you. There will be an instant-messenger style chat system, with separate windows for personal, party and clan chats.
Battle.net will allow you to group your friends' various characters and aliases together in a Facebook-style Real ID, probably under their real name, for easy identification. This will sit on top of, rather than supercede, traditional character-to-character friendships.
"Cloud play" will permit StarCraft II players to pick up their Campaign games and multiplayer profile from any computer they have the game installed on, without physically moving files from one machine to another. Your profile will track achievements, stats, match histories and so on across multiple characters and Blizzard games. StarCraft II achievements will unlock avatars, and decals which can actually be applied to your in-game units.
There will also be a friendly matchmaking system for all StarCraft II players. It will divide players into leagues from Practice with certain anti-rush rules and map sets, and a slower game speed, to allow new players to get accustomed through Copper to Platinum and then Pro leagues. Within a league, you'll compete with 100 other players in a "division" over the course of a season. Do well, and you can enter a tournament to see who wins the league.
Browsing for games will also be much improved, with grouping and filtering systems in place.
Watch out for more detail on StarCraft II and Battle.net in a full hands-on preview from BlizzCon soon.