"Arrival is a side-quest, ultimately," explains Jesse Houston, producer at BioWare, "but it's also kind of an epilogue," he adds, reiterating that it's the final Mass Effect 2 update. Within the context of the game's plot, players can access Arrival at any point after the mid-game Horizon mission. Depending on when players choose to undertake the mission, Houston notes, they could experience some "small differences," though he describes these as "aesthetic" changes only.
Though a side-quest, Arrival is different from other such missions in Mass Effect 2 in that it's strictly a solo operation. Shepard is on his (or her) own throughout the entirety of Arrival.
"Shepard's alone, through the whole thing, and that adds a layer of complexity," observes Houston. The challenge of Arrival is the absence of squad members. Players must handle the combat on their own, without employing team-based tactics, the core gameplay that Mass Effect fans have become quite comfortable and enamored with. The challenge for BioWare was to design this solo combat to scale to the player's level.
I previewed Arrival as a level-8 Soldier, and this particular Shepard was better equipped than some of the other classes to handle squads of grumpy batarians on his own. My one death occurred while charging into a particularly tense gunfight like I was John McClane, reminding me that even a Soldier-class Shepard is no action-movie hero. I can only speculate that other character classes will be even more challenged to use brain over brawn to survive. If you're an Adept or Engineer, for example, the hindrance of only being able to wear light armor could be a particularly difficult weakness to overcome -- I fought a lot during my brief playtime.
Tactful use of cover and a careful approach to each encounter is paramount. BioWare has actually added more instances of stealth into Arrival than found in the main game -- a plus for you Infiltrator Shepards -- though Metal Gear Solid this is not. I was able to side-step two potential fights by surveying the environment and finding a quiet way around. There isn't any tangible reward for being sneaky, but it provides an alternative to approaching the mission as simply a rote third-person, cover-based shooter.
While Arrival isn't the bridge that many expected and might have hoped would extend the endgame of Mass Effect 2, connecting it to this holiday's Mass Effect 3, it still shows signs of being a good piece of DLC. The mission seems to be on par with "Lair of the Shadow Broker" and "Project Overlord" in its scope and delivery -- an action-packed add-on that extends the universe in a meaningful way.