The effect of whipping of the backpack quickly to grab another lens while forgetting that the camera is still attached to it!
The OP recognises this potential problem: "My one concern is it being cumbersome when you want to take the backpack off and sit down." Speed things up and, potentially, accidents could happen. If your camera does not have interchangeable lenses then this may not be an issue - but the weight is not likely to be an issue on a fixed lens camera either.
Life is for living, cameras are to capture it (one day I will learn how!).