Gravity was a really enjoyable movie. The thing that I liked most about it is that the director did not fall into the trap of making it 2+ hours like every other movie out there. If you can tell the same effective story in under 1.5 hours, go for it. Those with short attention spans will appreciate your work :) Also, I have a new found crush on Sandra Bullock. If I were to get stuck in space with one chick, it would be her.