Output Quality Issues With iPhone4S Source Video

I've been practising with a Steadicam Smoothee and have been shooting some footage moving through a forest. If I play the raw quicktime files the motion is smooth, the edges of tree trunks and other objects are crisp as the camera moves past them.

After I bring the footage into Vegas Pro 11, there doesn't appear to be any format I can render to that gives me acceptable quality. The edges of trees buzz and vibrate, the overall image quality is bad and the entire effect of the smooth Steadicam motion is lost. I've tried WMV, MOV, MP4, AVC and YouTube all in several flavors. I've seen other people's Smoothee examples on YouTube shot with an iPhone4S and the quality of those videos is fine.

Has anyone come across this?