Arma 3 is officially in beta, with four new showcase missions, two new multiplayer missions, and a bunch of new vehicles -- helicopters, transport trucks, minisubs -- in tow. Full beta details follow after the break. The extra realistic military shooter/simulator is available through Steam and its own store. Purchases give you access to the present beta as well as the eventual full release.
My favorite addition over the alpha is the nighttime solo mission that tasks you with wreaking havoc and then slipping away, mostly because when I fail miserably I don't have to worry about the enemies seeing the look of embarrassment on my face.
I'm quite terrible at Arma 3, but I definitely appreciate the nods towards realism and higher stakes it carries. There's natural pacing in the running around and doing military things between actual engagements, chronicles by some amusingly stilted voice acting, and cowering behind a rock for ages is a welcomed strategy. Plus on one mission your squad mate keeps addressing a "Nichols," but it totally sounds like he's saying "pickles." I laughed every time. This is why I wasn't allowed in the military.
Key Features in the Arma 3 Beta