yeah they work,
i have one on my Atomik Fuse, also Rodney68 uses one on his lads Race bike
Chickenwingz just got and fitted his, and Blender is ordering one too.
they have a capacitor in the black adapter, this stores the peak energy that runs down the lead
and lets it fire this when the coil fires.
so it gives off the best spark each time it fires.
you can hear the difference at the spark plug, pull the plug and earth it to the head and kick it over.
then fit the lead and test it again, definately gives off a better spark.
you can fit them 2 ways, the original lead should just unscrew to remove it from the coil.
if it doesn't, don't force it as it may break the thread off in the coil.
if it wont unscrew, you need to cut your coil lead about 50-100mm short of the coil,
then push it through your new leads' adapter boot and screw it in firm.
the other way, which i used to fit mine, is to cut the lead about 100mm in from the adapter
and screw the end of the lead into the blank end
the other end can then be screwed into you coil housing, i needed to trim back some of the insulation so that it would fit into the coil housing, i used the bench grinder carefully to grind about 1mm deep, off the lead
and did it about 15mm's down the lead.