The problem i forsee is that people will complete it in under 10 hours. Not sure if it is worth it no matter how good the game is.
From what I've seen, it could be even less. It really depends on the luck of where the alien roams etc. Some could have a far easier play through than others. It's been commented on by various game journos, even with a short section of the game to play with, the time taken to complete varies a good deal.
Personally, I'd only be annoyed if I completed a game like this in under 3 or 4 hours.