Great
I loved the thing from start to finish. And don't worry about people saying it was "too short", they just need something to whine about.
There was one minor problem and that was the sound you used for the footsteps. They were extremely loud in the beginning, which I managed to look over in the hopes that you purposely did that...but what really bugged me was the fact that you only had one sound for it. This created some problems: first, there was no distinction between the two people walking...or even a difference on a step-to-step basis and that monotony was really distracting; and second, you should have used a different sound for the concrete roof than you did for the metal stairs, it was really awkward hearing those bassy steps when I was expecting a high-pitched, tinny sound...and again, each step would've made a different sound.
Well, there's your mini-lecture on footstep sounds. You can easily make a few by taking high heels and knocking them down on a nice piece of wood.