Starting today, Steam users may download full versions of these best-selling and critically-acclaimed games, including the complete DOOM series and QUAKE I - III, including mission packs, as well as id's pioneering PC side-scroller, Commander Keen and vintage favorites Wolfenstein 3D, Spear of Destiny, Heretic, and HeXen. As part of the id Welcome Celebration on Steam, select id packages are being offered with a 10%, limited-time discount.
The press release
has more details, including the full list of games that will be made available.
If anything was going to tip the scales in Valve's favour, it's probably this. They've built what is probably the best distribution system for online games (despite me having some extensive reservations about the system it is still almost unarguably the best option out there for gamers and publishers).