It is a good product. However, Pig Spit is as good or better. Pig Spit costs about 2/3's as much in a can nearly twice as big. Some Walmart stores carry Pig Spit.
I have never used Pig Spit, but I do use s100 engine bright all of the time and I really like the product and it is worth the money if you want your engine to look black. You do not have to use it every time you wash your bike because it does last for a very long time. It is not a scam from any manufacturer in my opinion, it is an essential for quality bike detailing in my opinion.
The Brightener works well, but it will build up over time (kind of like too much Armor All on your car tires), so make sure you do a good cleaning of the motor a few times a year.
What are you guys using to clean between the fins of the motor? Getting a lot of dirt build up from riding in the rain. I have the black engine on a 06 Street Bob.
Spray on simple green and use a paint brush to spread it around and "scrub" the dirt. Then hose off. I forgot, wet the cool engine with cold water before hitting it with simple green. I don't leave it on too long, maybe a few minutes.
It works well I have used it and will continue to till the can is empty. My riding buddy uses pig spit and comparing the 2 it appears the pig spit works much better