I dont think that will be the problem here, as the mercury is liquid, so will be very different to water hitting a solid metal.
Your probably right about complexity.. but then sapphire found a way round it.
Whats to stop this idea being used with jet impingement?
I think mercury would be much more expensive than a pump though
(O/T) Also I dont quite understand why heatpipe coolers have many sealed tubes, and never have a waterblock like thing, filled with coolant, with the pipes connected to it... wouldnt it be work a lot better?