I think if I had no choice but to take my bike across that bridge I'd probably do it at a much faster pace than that guy did it. I'm not saying I'd race across it, but I'd feel a lot more confident and in control at about 15mph than babying it across like that. Both feet on the pegs and looking straight ahead at the other end of the bridge, rather than waddling it across and taking the risk of losing my footing and dumping it.
I think the hardest part, as long as the bridge held, would be not letting the water moving under you screw up your sense of balance and motion. It would be really hard not to instinctively lean to the left to counteract the fact that your eyes would be telling you that you're moving to the right.
Okay, now I'm getting sick just thinking about it.