A few people have mentioned the engine running hot (other forums included), I can only imagine the fatter spark means that the timing might need to be retarded a little as you might think the burn will be faster if the initial flame kernal is bigger. Perhaps the heat range would need to change as well? Faster burn would mean higher peak temperature and pressure.

So far no one's said there's a good concrete benifit. Anyone tried the more far out plugs like halo, split fire? I remember seeing some jetfire ones that had the plug in an inclosed volume (prechamber). Might have to experiment myself....