I picked up a GoPro on the Woot sale a few weeks ago. I also have a ContourHD. IMO, the GoPro is the better "outside" camera, since it's armored, waterproof, and can handle wind noise FAR better than the ContourHD. The Contour produces a better image to my eyes though. The colors are less saturated, and since it uses a narrower wide angle lens, there's less distortion than the GoPro.
For driving videos, the Contour is my cockpit cam, and the GoPro will be my exterior cam.