Have them on both my FZs. The switch is not that great so I spent another $11 on a waterproof illuminated high power switch. Illuminated Seat Heater Hi/Lo/Off Round Switch
They work well if mounted right. Turn them away from the direct windblast.
Upgraded on my 06
It is only very slightly better and the O2 sensor has something to do with it. But with a K&N and laser quads my 06 felt smoother. Now I just have the K&N and a modded airbox and the on/off throttle nature is back slightly. But I like the smooth sound of the stock exhaust...