Out of my burst of 7 I had 3 that were about equal to the above pic. The first 2 were bad, but the next 3 were good and then he moved noticably so I instinctively tracked hime and blew the last one.
Granted though, 1/4 second is a bit extreme. The trick works a lot better when you need 1/500 but can only get 1/250 - chances are very good that you *will* get a good shot then. But 1/4 on an animal this close on a windy day would have shown problems even with a tripod. I've done stationary objects or large distant birds fairly reliable at 400mm 1/25 - again remember that the lens is IS, so that's really only 2 stops slow since 1/100 is just about always good at 400mm.