If I remember right, it's necessary to start ARMA II and ARMA II: OA once through Steam. After that, I think once you've got DayZ installed, then Six Updater, you do not need to use Steam to start it anymore (I don't). Just start it through the Six Launcher program. The Six Launcher will automatically update you with DayZ and ARMA patches.
I also setup a SLG Teamspeak server. Here's the info:
addr: 108.166.186.95:9989
pass: sunlitrocks