The Gabe Newell And Erik Johnson interview on Gamasutra has a note we missed last night, as Computer and Video Games points out an answer revealing that Portal 2 sold better on PCs than on console, and that the Xbox 360 edition of Left 4 Dead actually outsold the PC version. Here's word from Valve's Gabe Newell:

We can never predict; I mean we just try to build good games and then we tend to be surprised. Portal 2 did better on the PC than it did on the consoles; Left 4 Dead did better on the consoles than it did on the PC. So you know we don't try to guess, because we're not sure what value there is to guessing. We've never had a situation where we said, "We really, really want to build something that is more popular for the console guys." 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.