1. Ability to use the Steam feature "View Game info", see server IP and ping, see score, and maybe other features that ArmA3 has.

like here:
http://i.imgur.com/RrCWWmQ.png

2. When seeing player pool and server score have before or afters players names their Steam steam avatars. That whay you can find people you play/ed with in players list feature or recent games of steam because many of them have differant steam and in-game profile name.