Replying to Losing quality when editing

So I am a total noob at editing, when making the edit it ends up losing a ton of quality, it looks great in preview but the end product looks nothing like it.

example

Gopro Test Edit from Ryan Johnson on Vimeo.

Now I shot in 960, and made it an .avi file mjpeg compression. Now Pinnacle would only let me have it in 720 resolution, but that video seems to be alot less than that.

Help me in my n00bness please!