Helium, for the animation, it looks decently realistic. I'm not sure how I could critique it. Maybe one thing that you could change is have the letter flutter around a bit more rather than just settle after the first flit.
    One thing on the set though, before I saw the car drive by, I thought it was a roof top due the angle of the camera and looking down over the curb at the buildings. I realize that this was an animation test, not a set design test, but I thought I'd let you know.