Ive had these evil things on two different bikes. In both cases Ive found them to be both a nuisance and lacking in any kind of self discipline.
Back when I had the patience of youth I sorted the one on my CBR6 so that it dripped at a rate of about 1 drip per minute. Strangely enough it would suddenly accelerate as soon as I took my eye off it and the back end of the bike would be caked in that blue rubbish. So I ripped it out.
My current bike (Hayabusa) came with one fitted and it appeared to work very well for two weeks, I was a converted man and thought I had been wrong. Unfortunately I opened the garage door one morning to find the little bugger had ****ed all over the floor through the night of its own accord. I since turned it all the way down but I had another couple of instances of it chucking oil out randomly. Its soon to be removed and smashed to bits, a fitting end considering that could have been what my bike would have been in if the scottoiler had its wicked way.
Buy a chain now and then or fit the oiler and have it last ages with the risk of it ****ing on your back tyre? Easy choice for me