Bioware's MMO, Star Wars: The Old Republic, just launched on Steam.
The game originally came out in 2011, at a time when EA was trying to get its Origin platform off the ground and was loathe to release games on Steam. It's only recently that EA has been reintroducing its games to the platform, and today is finally The Old Republic's turn.
When it first launched, The Old Republic was hugely ambitious. A fully-voiced MMO that combined the decisions-driven storytelling of a single-player Bioware game with the large scale and social element of a more traditional MMO, many people enjoyed it more for its story than they did any of its live game elements.
While the core game is free-to-play, there is also an optional subscription available through Steam that includes a level cap increase, access to the Onslaught, Knights of Eternal Throne and Knights of the Fallen Empire expansions, and unlimited access to various game modes. If $15/£9 a month sounds a bit much, there is still an absurd amount of content in the free game to be getting on with as well.
The Steam release also has three cosmetic bundles available for purchase as well, the Jedi and Sith costume packs at a whopping $25/£20 each (or an even more whopping $60/£48 for the deluxe edition of either), and the Galactic Leisure Bundle that includes a holographic Rancor toy, Vulptilla pup pet and a Dejarik (the cool holo-chess from A New Hope) emote.
Keep in mind that the game still requires the external SWTOR client to be installed and running in order to play. This just lets you manage your subscription and installation via Steam should you prefer to.