After a conversation this morning with @asros i realized i’ve got a lot of info about the Mass Effect 3 Demo somewhere in my head that i should really write down for other people to see.
Please note this is a draft and thus has no particular formatting

How does the Mass effect Multiplayer Co-Op Demo Work?
You (the player) take control of a character (based upon (1) of (6) classes) and then with (3) others proceed to survive 10 waves of enemies while completing objective based missions. As you complete waves and objectives you earn experience and credits to level up your character and purchase recruit/veteran packs for items and character bonuses.

What classes can i pick from?
There are 6 with each class having roughly 4 (or 5 can’t remember) different races which vary up the playstyle for each. The classes include Adept, Engineer, Infiltrator, Sentinel, Soldier and Vanguard. Each class has its own strengths and weaknesses (i’m not going to go in depth about them. i don’t have all day to write and you don’t have all day to listen.)

What races can i pick from?
Not all races are available from the get go. Generally 1 human character (male or female) is selectable. The others are unlocked from Recruit/veteran packs. The races that are available though are Asari, Drell, Human, Krogan, Salarian and Turian.
All races have their own unique animations, voice work and limitations. The Turians for example have higher health and defense and weapons bonuses (which makes for an awesome soldier class work but they can’t dodge.)

How do i customize my character and what can i customize?
After you have selected your class and race, you can customize your character under the appearance menu selection. initially your limited to only a primary color and a highlight color. As you unlock class/race cards (wow that sounds bad) you get more appearance customization options such as a third color option (the underarmor), armor pattern selection and then suit light coloring.
Sadly, actual facial and skin changes are not available in the demo.

What how do i get new weapons, upgrade weapons and customize weapons, what kind of limitations are there for using guns?
Just about every weapon from ME2 and some new ones are available. just not from the start. Players start off with the same default equipment. The Avenger rifle, Mantis Sniper rifle, pistol, shotgun and submachine gun. New weapons and upgrades are picked up from Recruit and Veteran packs.
Weapons are selected from the weapon selection screen.
A player is allowed 2 weapons at a time. (be aware that weapons detract from your power recharge time. Bigger weapons subtract bigger amounts. So in theory if you are playing a powers based class such as the Adept or Sentinel you will want to use light weapons or a single weapon).
Weapon customization is done in the weapon select screen, with a particular weapon selected hit the customize button (on the xbox this is X) and it’ll bring up a unique looking window showing your gun laying on a bench. Mods are selected by pressing up and down to highlight Mod Slot 1 and Mod slot 2 and then hitting left and right until your mod of choice is shown. hitting the select option installs the mod and adjusts your weapon stats accordingly.
Weapon and Mod upgrades are unlocked through Recruit and Veteran packs and any upgrades are automatically applied. (for instance if you have a Mantis 2 Sniper rifle and unlock an upgrade your weapon is automatically upgraded to Mantis 3 with all stats boosted accordingly. Everything is automatic)

You keep mentioning Recruit/Veteran packs what are those and how do i get them?
One of the things that really sets MAss Effects Co-Op multiplayer apart from other games is that weapons and equipment can only be unlocked from item packs that are purchased from an ingame store. Think of it as like booster packs for the card games we played as a kid. Except half the cards are one time use only items.
Recruit packs generally upgrade your starting equipment and have a few 1 time use only items sprinkled in. very rarely will you have a rare card like a new weapon or a new class card.
Veteran packs include much more rare items such as one time use only equipment cards, weapon cards and class cards. Veteran packs is also much more expensive, costing about 20K credits verses 5K for a recruit pack.

You’re mentioning one time use only items, what are those?
One time use items are what you think, items that can be used only once but that can be stockpiled. there are two types of item cards. ones that provide equipment bonuses and ones that provide immediate bonuses.
Equipment Bonus Items provide a single bonus to either Armor, Weapons and Ammo that lasts an entire game. (1 game is 10 rounds, once you extract or are wiped out the item is used up). You can have up to three bonuses (1 for Ammo, 1 for weapons and 1 towards your Armor or powers at a time.)
Immediate Usage Items are items that provide an immediate affect and are only usable twice per game (although you can stack them past the allocated 2). I don’t know how its oriented in the PC version but the xbox version has them assigned to the DPAD on a controller.
In order – Up – One Time Use Missle that kills everything in its blast radius
Right – Instant Shield/health regen
Down – Instant Revive when you are downed
Left – Instant Ammo resupply.
These items are picked up from Recruit/Veteran packs despite being a limited amount are able to be stockpiled for future games.

When i look at match difficulty what does Bronze, Silver and Gold mean?
Bronze, silver and gold scales the difficulty in that order. Gold is harder then Silver which is harder then Bronze. As you scale up the difficulty you scale up the enemies you fight. However the rewards scale up as well. A typical 10 round bronze match will net you about 90K experience and 15K credits. A silver match will net you 130K experience and 35K credits.
One of the things i pointed out to @Asros that i think is crucial to know is that the difficulty does not scale well between 1-4 people. What i mean is that there seems to be the same amount of enemies when 2 people are playing a match verses 4 people. This can be rough for new players starting out who can’t get 4 people together for a match.

How are matches laid out?
There are 10 waves per match with waves 3, 6 and 10 being a variation on three types of objectives.
Objective 1 – Eliminate 4 Key Targets (this can vary but is generally an elite type for that wave. in the later waves this can mean a Phantom, Atlas or Combat Engineer. in the earlier waves its generally a Commando, Guardian or Nemesis type)
Objective 2 – Hack a central point. In this objective, you are tasked with wireless hacking a terminal. Basically all four (or however many you are playing with) all stay within a circle and wirelessly hack a computer. The Hack goes faster with more people in the circle and more exp is given as well to everyone involved.
Objective 3 – Hack 4 Key targets. 4 items are randomly placed through the zone that need to be hacked.
For Objective 1 and 3, the next targets are randomly selected AFTER the first target is eliminated or hacked. So you can’t jump out of order. You have to kill/hack Target 1 before Target 2 is available.
Also, the faster you complete the objective the more credits you get as a bonus.
Waves do not complete after you complete the objective. You must complete the objective and then kill all remaining enemies to go onto the next wave. However any credits you earned stay with you. (So you could complete the objective and then get wiped out and still get the credits and exp you earned up to that point)

The other 7 Waves are the standard kill all enemies while staying alive waves with the only rewards being experience, experience and more experience.

Random Question Time.

How do i create/setup/join matches?
There is several ways of doing this. The first is to randomly join someone else’s game, this will take you to a lobby where you can change characters, weapons, level up powers, purchase new equipment etc. However the problem with this is that its harder to play with friends since its all random
The other way is to create and host your own match and invite your friends. There is a bug or poor code design, however that prevents random people from joining your game (or it just takes a really long time to get others to join). However the game does support drop in and drop out so friends can drop in while the match is in play.

@kneedough Asks “How do you delete a character? Is it possible? What about unlocking classes? Is there a way to unlock no helmet or toggle it?”
At this time there is currently no way to delete your character, classes are unlocked through the Packs, and there is no way to unlock/toggle a helmet. If i had to take a guess this was to make it easier on the multiplayer system. Also Each class contains two human characters which have the same powers. One could in theory use one for one power layout and a second as an alternative. There is no way to reset powers but i’m sure Bioware has something planned for the future.

@krizhek asks “How long does a me3 co-op usually last?”
Anywhere from 5 minutes to 30 minutes depending on the skill level of the players involved. Generally a bronze match will be between 18-23 minutes. Silver Matches can range upwards of the 30minute mark. Unsure about Gold Matches. As your characters become more powerful and get better upgrades. The time it takes to complete a match drops to about the 18-23 minute mark. The fastest I’ve ever seen was 17 minutes.