I had one (Scotoiler) on the VFR - a great bit of kit, buy it now!! - if you do lots of miles get the one with the massive resovoir behind the licence plate. If you have any probs the actual tech support from the Scotoiler co is absolutely first class. I'm riding a Guzzi now - so no need for such things.

Make sure it is adjusted right - I once got it completely wrong and it was virtually pissing oil onto the chain which was spraying onto the rear wheel .

Adam