helmet cams

Anybody had any experience with helmet cams and can throw some light
on what to look for and what to avoid when purchasing? I was looking
at the GoPro one because the price is right but the video size is
512x384. Maybe it looks good on their web site but it will be too
small of footage that will look like blocks of pixels in full screen
mode. What size should be looking at if decent looking full screen is
my objective? If I only want 15 seconds of youtube hero/ow my balls
fame?