Super effective. Love the foaming aspect of the product as you can see exactly where it's applied. I've been using de-greaser products for years and WD-40 obviously knows how to make a great product. Smell is very pleasant as well without being obnoxious!
This degreaser foams up nicely & clings well, it might be ok for light duty jobs but I expected it to be far stronger. After I apply to the chain and cassette a few times I still see a bunch of greasy crud left in place which is difficult to get at with a brush which to me is the whole point of spraying something on. Overall, I was disappointed, I expected it to melt away the grease and grime more than it did for me. I prefer a stronger solvent like Finish Line Speed Bike Degreaser that blasts off grime, for really dirty jobs.
I was interested to try WD-40 Bike Chain Cleaner and Degreaser as an alternative to stronger citrus cleaners because of the advertised foaming action and water soluble cleanup (similar to citrus). I found that the foaming action did a good job keeping the cleaner on the drivetrain. However, the degreasing action is not as powerful as a strong citrus degreaser when it comes to cleaning a chain. WD-40 Bike Chain Cleaner and Degreaser leaves more grease and oil inside the chain than stronger solvents even after repeated applications. It does work fine as a general cleaner for surface grime on components and frame but does not penetrate to the hard to reach stuff. For that job, Finish Line Speed Bike Degreaser is a better choice.