One thing I learned the hard way about the VIRB. Don't start recording via teh side switch if you have it powered off. Apparently there is a somewhat known problem in which the GPS data gets out of sync with the video because it takes several seconds for the GPS to sync to the satellite while the recording of video begins.
All of my first 2 events recorded with the VIRB were out of sync, so I had to try and manually sync them which is a pain...
Otherwise the data is pretty cool once you get is synced.