I understand why the two halves of Penny Arcade apparently are almost at war at each over it; it’s… different. To give an idea, my gameplay involved [SPOILER WARNING]…
…going through two different runthroughs, then getting up and quitting the game at the urgent behest of a narrator. And not because I was upset; because I agreed with said narrator that this was the only way to ‘win’ the game. And I didn’t feel like I wasted my money on the exercise.
If I had to say what The Stanley Parable is I think I would say that it is a well-designed piece of intellectual property that has only a tangential relationship to a traditional game; and that it probably would not be able to exist without Steam. So put that in the plus column for Steam.