New here, but not to the Aliens franchise.
I got my pre-ordered copy of the game today, and have played through half of the campaign as well as trying out each of the multiplayer modes.
While IGN and Metacritic will have you believe that this is a terrible game with graphical issues and poor presentation, let me dispel any apprehension you may have right now. THIS GAME IS FANTASTIC!!
Critics are misguidedly looking for the next-gen FPS CoD-killer, whereas die-hard Aliens fans will be looking for a true sequel to James Cameron's Aliens. This game represents that, more than any movie-adapted video game I've ever played. Aliens: Colonial Marines is a stalwart example of atmosphere and story done right. With a wonderfully-crafted narrative and a deep, tension-driven, and exciting campaign just ooooooozing with all the fan service and spine-shuddering chills that we've been waiting for with an Aliens franchise game. No true fan will should be disappointed.
Gameplay-wise, you're looking at a campaign mode filled with tight shooting, dark corridors, and some superb voice acting including the return of several actors from Aliens including Lance Hendrickson and Michael Biehn. Weapons feel powerful and accurate, the arsenal of the true badasses that the Colonial Marines are (with the one notable exception of the Assault Rifle...with its wimpy 3-round burst, ineffectual sound design, and the fact that it's completely extraneous since the Pulse Rifle is better in every way). The sound design is dead-on, with everything from doors opening to motion tracker pings to pulse rifle blasts sounding exactly like their movie counterparts.
As for the Multiplayer (otherwise known as "why I will keep playing this game after i'm done with the 6-hour campaign"), the game offers some great sustainability in the way of many different game modes (all of which are teams of xenos vs. teams of marines; some of which the marines have only 1 life while xenos respawn constantly) and a TON of unlockable content for customizing your weapons and armor, xeno attacks, and appearance for both sides. The game modes offer a varied assortment of objectives and gameplay styles, and are a ton of fun.
As for the downsides....which every game has. As of today, the communications aspect of multiplayer is buggy (I tried chatting multiple times and the mike connection only worked about 1/3 of the time). There seems to be some lag or frame stuttering during mutliplayer matches during the downtime between rounds, but i'm not sure what caused it. All in all, any issues are minor compared to just how fun the game is!
The Verdict: 8.9/10 for me, the best Aliens game of the last fifteen years.