I’ve used it. Cant say it’s any better or worse than anything else.
But it’s certainly better than Water Displacement Formula 40.
Can’t stand for WD-40. It stinks and it’s good for much. If you need a good penetrant, buy Kroil.
Wd-40 is excellent at certain tasks, but
not good at long term lubrication or rust prevention. I do not use WD-40 on any firearms at all and would never recommend that anyone else do either as it will over time get sticky and goopy! It is a water displacing fluid, not truly meant for guns, lubrication or mid to long term protection.
OK - that said, WD-40 is excellent as a cleaner on tar, grease, very minor rust, crud and build-up. If you get road tar on your car or wheels, WD-40 is the ticket. WD-40 also works well in cleaning all kinds of fingerprints, smudges etc, off of stainless steel. WD-40 can also remove certain annoying stains and marks that the Grandkids can impart with crayons, markers, etc. It's also great for cleaning pitch and plant goop off of gardening tools, shears, blades, pruners, saws etc. before sharpening and lubrication.
I have at least 7 or 8 cans of Kroil, Liquid Wrench, PB Blaster and a few other penetrating oils. Quite honestly, those will help loosen rusted parts, nuts and bolts better than WD-40 most of the time, but IMO they just don't live up to the hype either. For really stubborn rusted on bolts, nuts or screws, heat is usually your best bet if it can be used in that situation.