Tried Insurgency Sandstorm for the free weekend.
Did the tutorials and i like the gameplay, shooting feels really good, even though the setting is kind of boring, but i couldn't figure out how to play with my buddy in a private coop game, and couldn't set up a working LAN.
Now granted, i'm pretty fucking distinguished mentally-challenged fellowed, but i still don't understand why something so simple has to be so convoluted, ffs.
Even googling, leads you to a bunch of confused steam posts on the matter.
Unfortunately i don't give a shit about playing with strangers, so i probably won't bother (doesn't help that the game seems to dip my GPU into lava).
EDIT: Also i hate the invite system Steam has, half the time the pop-up with "Join game" doesn't even come up.