Edit: OP now updated with correct multiplayer information, so please disregard this post. 
I scoured the Internet looking for information about the multiplayer. Unfortunately, there's absolutely no official info, so what I describe here is what I've gathered from watching videos, reading previews and browsing the official forum. If any of you see any incorrect information below, or know something more, then please don't hesitate to post here.
First, you choose your loadout before matches. You get three loadouts that you can customize and save. You can change between them during a game, and can also edit them mid-game. There's 15 points you can spend on each loadout.
These are the known weapons and accessories you can choose from:
Weapons
Pistol - 1
Combat Shotgun - 2
Submachine Gun - 3
Hammerhead - 4
Automatic Shotgun - 5
Semi Auto Rifle - 7
Assault Rifle - 8
Sniper Rifle - 9
You start with a primary weapon as well as an optional secondary weapon. In addition, there are four power weapons on the maps:
Napalm Cannon
Pulse Rifle
Laser Gun
Rocket Launcher
Armor
No Armor - 0
Standard Armor - 4
Heavy Armor - 8
Armor decides your class, which can be scout, grunt or tank. Scouts have no armor, but can carry more, while tanks have heavy armor but can carry less. Heavier armor also means you move more slowly.
Explosives and Health
Shock Grenade - 1
Incendiary Grenade - 2
Frag Grenade - 3
Medkit - 3
Proximity Mine - 4
There's no limit, besides available points, on how many items you can carry.
According to IGN, you rank up by earning XP playing matches. They claim ranking up will unlock more weapons and accessories for your loadout, but early reports from people playing the game seems to indicate that XP and ranking up is only for the leaderboards.
The health system is slightly changed from single player campaign. Your armor still degrades, but the health is rechargable. But according to IGN again, it recharges much more slowly than in similar games (which I guess is why there's the medkit option in the loadout).
There are six game modes:
Deathmatch and Team Deathmatch
Blitz - capture the flag, where the flag leaves a trail
Failsafe - search and destroy, where you plant bombs on control points with one attacking team and one defending
Control - king of the hill, where you can control up-to three different points on the map to increase your team's score
Armored Front - like Control, but with five control points where all must be controlled in order to win and where each team has one Mech
The game ships with nine maps, where three are for Armored Front only while the last six maps are for the other five modes.
To play, you can choose between a quick match or you can search for a custom game, which allows you to search for a specific game mode or map, which gives you a list of servers. You can also host a game, ranked or unranked. When hosting ranked, you can decide what game mode to use, map, and the number of players. Hosting unranked will give you all that and more, such as friendly fire settings (which are off in ranked), round time limit, team balancing, etc.
I'll add multiplayer info to the OP when it's confirmed (ie. the game is out and you guys have had a chance to play it, as we're not getting it here in Europe until Friday).
I scoured the Internet looking for information about the multiplayer. Unfortunately, there's absolutely no official info, so what I describe here is what I've gathered from watching videos, reading previews and browsing the official forum. If any of you see any incorrect information below, or know something more, then please don't hesitate to post here.
First, you choose your loadout before matches. You get three loadouts that you can customize and save. You can change between them during a game, and can also edit them mid-game. There's 15 points you can spend on each loadout.
These are the known weapons and accessories you can choose from:
Weapons
Pistol - 1
Combat Shotgun - 2
Submachine Gun - 3
Hammerhead - 4
Automatic Shotgun - 5
Semi Auto Rifle - 7
Assault Rifle - 8
Sniper Rifle - 9
You start with a primary weapon as well as an optional secondary weapon. In addition, there are four power weapons on the maps:
Napalm Cannon
Pulse Rifle
Laser Gun
Rocket Launcher
Armor
No Armor - 0
Standard Armor - 4
Heavy Armor - 8
Armor decides your class, which can be scout, grunt or tank. Scouts have no armor, but can carry more, while tanks have heavy armor but can carry less. Heavier armor also means you move more slowly.
Explosives and Health
Shock Grenade - 1
Incendiary Grenade - 2
Frag Grenade - 3
Medkit - 3
Proximity Mine - 4
There's no limit, besides available points, on how many items you can carry.

According to IGN, you rank up by earning XP playing matches. They claim ranking up will unlock more weapons and accessories for your loadout, but early reports from people playing the game seems to indicate that XP and ranking up is only for the leaderboards.
The health system is slightly changed from single player campaign. Your armor still degrades, but the health is rechargable. But according to IGN again, it recharges much more slowly than in similar games (which I guess is why there's the medkit option in the loadout).
There are six game modes:
Deathmatch and Team Deathmatch
Blitz - capture the flag, where the flag leaves a trail
Failsafe - search and destroy, where you plant bombs on control points with one attacking team and one defending
Control - king of the hill, where you can control up-to three different points on the map to increase your team's score
Armored Front - like Control, but with five control points where all must be controlled in order to win and where each team has one Mech
The game ships with nine maps, where three are for Armored Front only while the last six maps are for the other five modes.
To play, you can choose between a quick match or you can search for a custom game, which allows you to search for a specific game mode or map, which gives you a list of servers. You can also host a game, ranked or unranked. When hosting ranked, you can decide what game mode to use, map, and the number of players. Hosting unranked will give you all that and more, such as friendly fire settings (which are off in ranked), round time limit, team balancing, etc.
I'll add multiplayer info to the OP when it's confirmed (ie. the game is out and you guys have had a chance to play it, as we're not getting it here in Europe until Friday).