It really isn't hard to hand shoot the lens... and often I feel that people saying it isn't sharp are really talking about that they manually focused a little off. But the trade off of compactness, light weight, and overall portability is the reason to use the lens; the 100-400mm is anything but.
I find it extremely silly though, that you all are doing little more than bandwagoning "eww, donuts" when some of these shots do well at minimizing those donuts and focusing on the subject. Others... well.... yeah, you really need space between your subject and the background; but not all of them are bad, and many are rather nice.
Remember, the number one rule in photography is that it is not the lens you wish you had on you, but the lens you have, that you work with. If you want to lug the 100-400mm around and are fine with that, then that is your style of photography and nothing is wrong with it. But if you generally handshoot and enjoy keeping a light pack of smallish lenses... that's the market here.
No one lens is perfect, but the 300mm reflex lens does have its own niche.