The 'back' gesture is a piece of shit. I'm forever accidentally setting it off when trying to swipe to the next photo or drag something from near the edge of the screen, it's lost me browser tabs I'd just opened. Swiping left/right is too common an action to be an OS-level gesture.

Edit: since having the above whinge I've found the option to turn down the sensitivity. I'll see if that makes me a bit less 'old man shouts at cloud'.