I always sharpen them shaving sharp, but I am not at all certain it is all that critical. Sharp enough to cut is probably OK if you put the arrow in the right place and if not, then sharper won't make enough difference to make up for the mistake.
I shot four last fall and the distance they moved after the hit varied from six feet to over 200 yards. All the shots were dead perfect. Three heart shots, and one dead broadside just above the heart which cut the heart loose from the lungs and almost left it loose in the chest. Obviously, all four dropped blood pressure to zero instantly. The results varying so widely with very sharp blades tell me that sharpness is not the major concern to worry about.
The arrow results match what I have learned with rifles. Shoot 'em in the right place and they can still go a ways, or they can drop in their tracks. The deer arrow shot through both lungs that severed the heart loose from the lungs made it 200 yards pumping huge spurts of blood with every heart beat. How the hell does it manage that distance I cannot guess. I have killed a lot of deer whose wounds produced no blood pressure and couldn't make 100 yards, and never saw one get close to that distance. You wouldn't think that with a double pneumo-thorax and no BP they could make any more than the normal 50 yards or so.
