According to Valve, PC users dig portals, while console gamers are more into zombies.
In the modern gaming landscape, a multiplatform release usually does better on consoles than it does on PC, but according to Valve founder, Gabe Newell, the opposite was true for the eagerly awaited Portal 2, which actually found the most success among the keyboard and mouse crowd.
Newell used the game as an example of why Valve doesn't pigeonhole its games into "console" or "pc" focused brackets. He said that it was impossible to predict where the strongest reaction to a particular title would come from. He said that Left 4 Dead, another recent Valve title, had been a bigger hit with console games than PC games. Ultimately, he explained, Valve just tried to make good games and then see who liked them.
"We've never had a situation where we said, 'We really, really want to build something that is more popular for the console guys,'" He explained "Because usually we have a bunch of other higher priority problems we want to solve. So we're glad that people want to play our games wherever they want to play."
If Valve really doesn't ever discuss lead platforms and optimization, then it's probably unique among developers in doing so - or indeed, not doing so. Of course, it doesn't hurt that it makes games that translate so well to different platforms; if it made hardcore historical turn-based strategy games, it might have a little more trouble.