Originally Posted by northwind

Whether there's any power or performance improvement, i don't know... But they definately seemed to make my bike more eager to start on cold days. I replaced a 1000-mile old set of NGK standards with the iridiums and instead of labouring to start whenever there was frost on the ground, it more or less jumps into life. Those plugs are something like 6000 miles old now and still spot on. They're supposed to be less susceptible to fouling too, though you have to try pretty hard to foul an SV plug...

I'd probably buy them again, just becaues my creaky charging system needs every bit of help it can get to start on a cold morning