Most of the people's here think this is a timed contest! WTF?
Do you people go to Blockbuster, rent a movie, and fast-forward through it?
I don't care how good you are, powering through the game quickly is (ironically) a waste of time.
Now I know why people think it's not that good...they "beat" the game rather than "play" it.
PiTiFUL and dsm, I concur with what you two wrote, you seem to be playing the game the way it was meant to be played.
Back to the topic question:
I haven't finished yet. Been at it for about a month, play about an hour per day on average (generally a level per night) plus tweaking, and occasional multiplayer. Should be to the end in a week or two, no hurry. Looking forward to Nightmare!