Most people buy GoPros for the video quality/durability. even with microphone not being that great it's still a great deal IMO. for $330 you are getting HD video in a durable setup. Plus the wifi remote that interacts with the built in wifi so that you can turn it on remotely. Also you can dowload Cineform for free, their editing software and their app for iphone/Android that lets you view what the camera is viewing.
Previously to get the remote control it was an addition ~$100 (IIRC) add-on that you had to attach as a 'backpack' to the GoPro. And to be able to see what the GoPro was looking at was another ~100 (IIRC) add-on that you again had to attach as a backpack to the GoPro. But you could only only attach one add-on at a time. so you couldn't use the remote control if you had the LCD backpack on. Also you couldn't extend battery life by adding the battery 'backpack' add-on. But with a Hero 3 Black edition, the wi-fi is built into the camera so no need for that backpack. You can view through your phone if you want so no need for an LCD screen (though they do sell a LCD screen for the Hero3 that has a touch screen feature). So you can add the battery 'backpack' on extending you video time and be able to control and see what your Hero3 is doing. plus you can delete, upload your videos from your phone.
http://gopro.com/software-app/gopro-app
http://gopro.com/software-app/gopro-studio
Personally I think it's a good deal.
most of the time the audio is low from what I have seen is when the vehicle is moving ~20MPH or faster (including personal experience with my Hero2) and the wind noise drowns out most of the other noise.
Here is one of the videos I took my GoPro Hero2 in 720P at 60fps.
http://www.youtube.com/watch?v=KfRGDr--aAc
it's my 2004 Crown Victoria LX Sport and yes the camera is facing backwards. a group of SoCal Crown Vics met up at El Mirage for some legal high speed runs. hit the speed limiter at 110MPH whereas the guys with Police Interceptors hit the speed limiter at 130MPH. Notice the wind noise. This is with the waterproof case to protect the camera from the elements.
I like my Hero2, would like to upgrade to a Hero3 Black edition sometime. but there are other things I want to get before upgrading.