Scottoilers are worth every penny IMO. My chains never stretch and last much longer.
Poorly maintained chains can be dead in under 8,000miles, well maintain chains will last longer but is quite time consuming and chain loob is about £8 a can. New C&S is the best part of £100, thats without fitting.
Scottoiler oil bottles cost about £6-8 and last for ages. Wifes 636 has done 16,000miles and still the original C&S, which have probably been adjusted about three times. Still look like new, although I've noticed some slight hooking on the rear sprocket now.
They're probably not worth the cash if you do 1,000 dry miles a year, but worth every penny if you do more, especially in the wet. They need slight adjustment depending on the time of the year simply because oil flows better in warmer temps, so the flow rate needs to be reduced, takes about 10secs in Spring and another 10secs in Oct/Nov.