For the many who think GoG is the answer to Steam......it may be but not for Linux gaming yet.
When GoG releases a bunch of Linux games especially in their sales (which I get a bunch of emails for) And I have not seen many Linux games in their sale emails.....then I will consider switching. But consider this......I have over 200 games in my Steam library. Unless GoG is going to connect to my steam account and give me the games there for free.....it is not worth me switching.
Edit
Oh and for those bitching about Steam overcharging them for arma 3.......most likely it wasnt actually on sale at the time of the purchase. I just purchased a gift copy of Arma 3 Extended Edition for $37.50 and paid only 37.50 via Paypal. If it was on sale, it was a glitch and will be handled by the billing support team. Have a little faith since any company worth its salt takes fraudulent charges seriously. If still miffed, purchase it straight from http://store.bistudio.com in the future.