Yeah bought this on Boxing day... Would have been rude not too. Was just about to post it on here as I haven't logged in since the 24th but just saw this thread.
Also bought Portal for the same price as I figured for £3.49, it don't matter how long or replayable it is.
I picked this up while the offer was on, along the the Valve Complete Pack. Beautiful game, certainly worth the money, although I am finding it hard to get into; I don't much like the gameplay.
Great atmosphere, but not nearly enough ammo. Maybe I'm the sort of player who uses ammo as much as possible, but a game ought to cater to this sort of person.
That's sort of what I noticed, which is a bit of a problem, because that is what it is. The design is great, really atmospheric, and there's plenty to do, but there are times in it where you curse the lack of mindless violence potential.