Joining a friend in game is bad.

It doesn't work at all.

I don't know where I should post this. But it's terrible to not be able to easily join friends.

It works pretty reliably for me.

Open the Steam overlay, right-click on your friend, select join game. I believe they need to already be in a group, or have clicked the "create group" button before playing.

The most likely reason for this to fail is if the server your friend is playing on is already full.

It fails all the time. Even if my friend is in my party and I join a server, them clicking the "Join Party" button doesn't work. It's a joke. They can't even join off me through Steam. Pretty bad.

Works perfectly. Create the squad in the lobby before going into a game.