Honestly, the story is linear so if you play through it once you will basically have seen everything. But with the added difficulty levels the game becomes even more fun the second time through, plus you will discover a lot you have missed the first time through. So for a gamer like Game Foucs, this type of title will have plenty of replay value even a couple of years from now, when hopefully they will see the sequel or prequel to this epic game.
Buy it. Do not think about it, just buy it. The game is simply amazing, the best survival horror game in years and maybe ever. This again proves how great games can be when done by competent developers who have a clear vision and understand how to give gamers the best experience possible.