Congrats on going Mac but keep in mind that the GoPro and Contour are not like other cams and certainly not on par with even the less expensive AVCHD cams. However, it is also not a DV cam either, though there is a setting in them for that. I would never suggest you shooting in DV mode as there is no market for it and, just in case you ever needed a project in SD, you could always downconvert the HD footage to SD. If you shoot in SD, you're stuck with it.
In order for you to import the footage from either cam, download MPEG Streamclip, a free and bug-less application. Drag your clips over to the MPEG Streamclip interface window and then export to a folder in whatever codec you perfer to use,(for the GoPRO I would suggest Pro Res LT)
Then you can open FCP and import the files that MPEG Streamclip made for you. If you are working in FCE then you will be stuck exporting your GoPRO files using the Apple Animation Codec as FCE doesn't have the better and more useful codecs. I haven't even looked at iMovie in years so I have no idea what codecs it works with but know that there is a difference between the terms 'format' and 'codec'.
Give MPEG Streamclip a try, you'll like it despite the extra step in terms of pre-importing.
Steve