I think Mass Effect 3 is honestly some of the best multiplayer that I have played in quite a long time. It's challenging, it's dynamic, you need to use teamwork to succeed, and so many of the design decisions add depth to the combat.
When you first start the game, you have access to all six classes. Each class has 3 races; you get a Male and Female Human and then you get 2 of the following races depending on class: Drell, Krogan, Quarian, Salarian, Turian, and Asari. So for example, a Vanguard can be Human, Asari, or Drell and a Soldier can be Human, Krogan, or Turian. However, when you first start, only one human (Male or Female) is unlocked for each class. You must unlock the other two races and the other human sex by playing the game. Now, what is interesting is that each race of the same class has different abilities. For example, Human Engineers have Combat Drone while Quarians have the new Turret. What I truly appreciate though is that when you gain experience you gain the experience as a class, rather than a race. Therefore, if you play heavily as a Human Sentinel, and then unlock Turian Sentinel when your Human Sentinel is at level 10, your Turian Sentinel starts at level 10.
So that begs the question? How do I unlock classes? You do it by purchasing Booster Packs.
<running of feet>
NO! NO! NO! Come back! Not micro-transactions. When you play the multiplayer, you earn credits. You use these credits to purchase packs. Packs can contain the following:
1. 1 use items
2. 1 use equipment
3. New Weapons
4. PERMANENT weapon upgrades
5. Weapon Mods
6. New Races
7. Race Customization Options for existing classes.
There are in the demo three types of packs. A free starter pack, that you get only once. This, as far as I can tell, usually contains 1 alien race (Mine was Krogan Soldier) EDIT: This is NOT true apparently, you may end up with an new weapon instead of a race. Then there is a pack that costs 5000 credits and gives you a bunch of 1 times use items and sometimes uncommon items. Then there is a pack that costs 20,000 credits and gives you LOTS of 1 time use items and guarantees at least a uncommon item.
1 Time Use Items: There are 4 types of 1 time use items. Spare Thermal Clips, Cobra Missiles, Medi-Gel, and Survival Pack. You can have as many of these as you stock up on, but you can only take two of each with you into a mission. Thermal Clips completely refills your ammo if you run out. I don't use these often as I usually park myself by an ammo cache. Cobra Missle is the standard heavy weapon. Survival Pack will completely refill your shields and health, provided that you haven't been knocked out. Medi-Gel will refill your health if you HAVE been knocked out and ally cannot get to you (Provided an enemy has not executed you).
1 Time Equipment is applied before the game starts and persists for the whole game. You can use Ammo Powers, Armor Powers, and Weapon Damage Enhancements. Once the game is over, you lose these.
New Weapons: You start the game with one of each weapon. This unlocks different weapons.
Permanent Weapon Upgrades are exactly what they sound like. When you start the game, you have the level one version of each weapon, so for example, I started with a Mantis I sniper rifle. When you get the upgraded version (Mantis II) it replaces it permanently for all classes.
Weapon Mods: Exactly like they sound, each weapon can take two mods.
New Races and New Race Customization: These are cards you get in your packs that will either unlock new races or give you new customization options for a race you already have. Regardless of what type you get, they all also give you an experience boost for that CLASS.
Example: I started my game and got a card that gave me 12500 Soldier Exp and unlocked the Krogan Soldier.
Later on, I got a card that gave me 12500 Engineer Exp and Unlocked a new customization option for the Human Engineer. What this means is that when you first create your character, all you can do is name them and change the primary color and highlight color of your armor. When you unlock new customization options however, you can change the secondary color, give the armor patters, put lights on it, ect.
When it comes to playing the actual multiplayer, it's basically Horde Mode with intermittent objectives. There are 10 Waves + 1 Extraction Wave. The waves get progressively harder and the enemies more diverse. Usually it's just your stardard "Elimintate the waves" gameplay, but occasionally you will be tasked with an objective for a round. Those range from: Killing 4 Enemy VIPs (very hard, you only get about 1:30 per VIP), Shut down 4 enemy consoles (More difficult with less players as one players must "Defuse" the console) and Defending one friendly console while it uploads.
I really like how the game is built around a diverse team. If you go in without having at least some crowd control, some damage dealers, and some debuffers, you're probably going to have tough go of it, if not straight lose.
Different enemies present different challenges. Standard mooks and Centurions will try to flank you, Guardians will move up on you with their shields, Nemesis will keep you pinned down with sniper fire, Phantoms will cut the crap out of you, and Atlas will just soak up your delicious, delicious ammo while lumbering forward dishing out punishment (While all the other enemies flank).
I love that weapon weight affects your cooldown speed. That way, you're not limited to what weapons you can use based on your class, but you're still balanced.
I find that for a good go-to class, choose Engineer. Combat Drone is REALLY good. REALLY GOOD. Also, if you cast it behind a guardian, they turn around and shoot the drone, making their shield useless! Furthermore, if you're human, you have access to Overload AND Incinerate, making you quite good at taking out both armor and shields/barriers.
You WILL suck when you first start out. You will be level one and you will have crappy weapons. Play Bronze, level up and you will get better. I promise.
I dislike that the difficulty does not scale with the number of players. You need at least 3 to be effective. It's Technically doable with 2, but I doubt you will succeed often.
Do not be afraid to use your 1 time use items if you think you have a shot of winning the game. Winning the game gets you LOTS of credits which you will use to replace the items you used. If you stand a chance of winning and need to use a 1 use item, USE IT! However, that doesn't mean ALWAYS use them. If you KNOW you are going to lose, using a Medi-Gel to stand up and get killed again is a waste. Assess the situation and act accordingly.
There is NO penalty for losing. You keep all the EXP and Credits you earn up until you lose. The only time you ARE penalized is when you leave the game; leaving the game means you lose ALL the credits and EXP you earned that game. Games take about 20-30 minutes, plan accordingly. Leaving not only wastes all the time you spent playing that game, but also puts your teammates at a disadvantage. Don't be that guy. (DISCLAIMER: If your dog, house, grandma, baby, or other important thing/person in your life is on fire/some other form of serious peril/distress, then you should probably, you know, leave and take care of it. We'll understand).