First of all, no matter if you bought from Steam or a boxed edition they all use Steam for multiplayer. Apparently, that is not working currently.
However, multiplayer is not exclusive to Steam. Look in your game folders and you'll find the sim's manuals in PDF for several languages. Go to the multiplayer chapter and you'll see that while Steam is used for mutliplayer, flying online is not exclusive to Steam.
So, if Steam doesn't get the ball rolling on this one we can still join directly by entering the server's IP address (i tried it the other day and it works fine), plus it will also be possible to use 3rd party software like Hyperlobby (the manual clearly says that).
I think that even if the Steam-integrated server browser worked as it should, there wouldn't be too many servers up at this early point: a lot of people still optimizing the game, we are waiting for some major patches, the western hemisphere doesn't have the game yet, etc.
Long story short we can use whatever we want, it's just a matter of time before multiplayer starts rolling properly.
