Most tabletop games are built geared for two players. The rules are balanced and tested in the most typical type of game you as a player will be exposed to and the rules "work." When you introduce multiple players with most games you'll find some type of breakdown of the system. Most of the time the worst breakdown is the guy that goes first/last getting beat on by every other player or you have a "vulture-type" player that hangs back and swoops in to feast on everyone's scraps. In other systems with limited resources (like Malifaux) you run out of steam mid-way through your activations with four or more players and either leave yourself open to attack or have to be miserly with holding your cards until you MUST use them. And of course there are the systems where one player can quickly run away with a lead that's nearly impossible to catch up to (Necromunda mulit-player).
If games address multi-player at all it is typically shoehorned in late in development or applied after the fact to sell another expansion/optional ruleset. While this is cool that a game takes the time to cater to gamers that like multi-player the adjustments to the rules don't always equate to a balanced game. Most of the time the games are fun, but homes rules become a requirement so there is a lack of consistency when you travel to other places and play multiplayer.
Now that that's out of the way let's get to the point. Earlier this week I had a chance to play a three player game of MERCS. I played KemVar, maverickman played FCC, and breadcrab played USCR. This was really only my second time playing a full game, so I'm still picking up the tactics and learning the ins and outs of the system. We played 5 man teams and decided to just try and kill each other, last man standing wins.
What impressed me with the game at this level is it truly simulates a firefight (or at least what I imagine one would be like). Getting into a favorable position and overwatching is key to being able to put out a ton of potential damage. Most of the time shooting on your turn is the last thing you want to do, since it's incredibly hard to hit unless you can rack up a bunch of modifiers. Several time we had our heavies in favorable position and triggered each others overwatch to blast away at anything that moves. Because the firing numbers are so high it's not as broken as once might think (unlike Necromunda, where overwatching has the same chance of hitting regardless) because moving targets get bonuses.
The other thing that was interesting was rolling initiative for each guy. Because it's random you have less control over combos with certain models, which means the "last guy going is screwed syndrome" doesn't happen to the same player over and over again (unless you roll terrible).
To me the multiplayer game of MERCS is more fun than a two-player game because it limits the amount of running and hiding and forces players to get involved in setting up good firing positions. In multiplayer there can be moments of hilarity such as a USCR jumping on a EMP grenade so a Kemvar Sniper can shoot a tag to push someone off a building and other silly things that add another level of fun to the game.
As I said in my initial impression of the game, you need to play a few demos and a few games before it clicks. But once it does I think most players will find this to be a challenging fun game. Not so much if you like lining up hundreds of models and removing them the following turn, but for a sci-fi type skirmish game this is much better than the other systems I've tried and it's fast enough to play between other games.