Battery, battery, battery
I use one of these on my cycling commute (GoPro3). They last about 1h 15m I reckon, but I believe environmental conditions have a part to play: it's sometimes not lasted a slightly slower commute of 1h 5m (I'm normally 5-10 mins faster). I have it recording a rolling hour at 720p wide 60fps.
The first thing I do is to make sure it's left to charge off my PC. This is a major part of my defence on the road (yes, I obey the rules; yes, a minority of others don't; yes, they annoy me too, etc.) so I'd be interested to see how this new model operates in low light. Still, mine's working fine and I don't fancy forking out £350+(?) for a new one just yet.