I can give a review, but it will not be unbiased
There is a customer reviews page on the site, or you can google and find others.
The system works really well. Just fill the reservoir and ride. It is self priming and when you first use it it takes about 30-50 miles to for the oil to work it's way through the flow restrictor, so it's best to oil the felt pad before the first use. After that not much is required other than refilling the reservoir.
The oil starts to flow at about 40-50 MPH, so if you only ride in city stop and go traffic or trail riding on a dual sport your chain will not get much lube and you may want another solution. Usually getting over 40 MPH isn't an issue on a motorcycle.
On average it puts out about 1 drop every 2 miles.
The felt pads last nominally about 5,000 miles and they attach to the chain slider with an oil resistant silicone adhesive and are very secure. The side plates will wear into the felt pretty quickly until the roller makes contact and then the wear slows way down. Since the oil is applied to the inside radius on the chain, centrifugal force distributes it to the rest of the chain. The felt is a really clean way apply the oil, but as with any continuous lube system, you will get a small amount of fling. Mine mostly is around the front sprocket area. The felts come in thicknesses from 1/4" to 5/8". 3/8" is about right for the 919
I rarely need to clean or adjust the chain. I will just wipe the chain down to clean it every couple of thousand miles. You can even squirt some WD-40 into the felt pad and go for a ride and it cleans it pretty well.
I have used motor oil, bar and chain oil, and gear oil. The bar and chain oil is a little tacky and attracts more dirt. The gear oil has worked best for me.
Overall a chain oiler is one of the best mods I have done in terms of increasing enjoyment/ reducing maintenance.