For you guys playing on PC with decent rigs, check out the DirectX 10 and 11 mods for improved visuals:
AliensDX10 and 11 HD Better Grafik and Lights mod for Aliens: Colonial Marines - Mod DB
I've been enjoying multiplayer quite a bit, and find myself quite addicted to the Survivor mode. Survivor requires teamwork and strategy, and can be really fun with a good group of people.
Marines have to do things like seal up doors, activate security shutters, deploy sentry turrets, install motion detectors, and revive other Marine players if they get incapacitated. Marines do not respawn, and it is game over once they all go down. Smartguns, flamers, and rocket launchers can be found (or picked up from downed Marines) as well.
Aliens do respawn, on a variable timer, and have to work together to try to swarm the Marine defenses. It can be tough, and the aliens tend to die a lot, but I have a ton of fun trying to figure out better routes past their defenses, being stealthy, and taking out sentry guns and such. The aliens get better to play as you rank them up and unlock abilities. Higher rank aliens are pretty deadly.
The smartguns are great, but I can absolutely see why they limited them. They are fairly over-powered.