Tested on several very greasy surfaces in a seasonally-commercial/heavy everyday residential kitchen. As it's a heavy-duty product, I only used it on those heavy-duty occasional jobs.First, tested it on was a wall that gets a lot of Pam overspray because it's behind the heavily-used waffle maker. I wasn't impressed until I tried some regular cleaner for comparison. I used Johnson commercial degreaser at recommended spray-and-wipe strength, then double and triple that. It was like water. The Grez-off needed elbow grease and 2 applications, but it cleaned the wall completely, whereas the regular cleaner even at 3x had no effect. Also did a great job on the exterior of waffle maker that I'd almost given up on.It was aces on the stainless commercial stove backsplash and work shelf, which had been neglected and were very sticky with baked-on grease. They get a regular once-over with standard (in other words, weak, but no-rinse) household cleaner, which has little effect on the baked-on grease caused by an always-hot commercial stove. This is an older model 6-burner Wolf with plenty of use/abuse, and it did a great job (I'm a little perplexed at those with household stoves who say this didn't work--maybe the wiped it so quickly it didn't have time to work? The instructions do recommend letting it soak in...). It does require rinsing (just a wet rag was fine) and I'd recommend drying as well on stainless surfaces, or you will get pronounced streaks and spots. It did a respectable job on the iron burner plates as well.There were a few spots on the commercial sink that I'd never gotten completely clean before (used, came from a hospital), even with steel wool, that this shined right up!Excellent on painted cabinet surfaces--but I'd highly recommend it only for spot cleaning (spray one spot, wipe immediately) or applied to the rag and wiped, as it is very strong and will leave streaks on your paint if you spray it across a vertical surface and wipe it all at once, as you would cleaning a window. It removed both kitchen grease and some old adhesive I'd previously failed to remove with cleaner and a razor. Again, rinse. It's not everyday cleaner, and should be rinsed full-strength.I'm not taking off a star for the heavy smell, since it's advertised more as a garage-y degreaser, and does have smell appropriate to heavy mechanical use (all super-concentrated degreasers are stinky; that's why you use the nice Mrs. Meyer's stuff for everyday), but I did take off one because it runs rapidly, making it less effective for vertical surfaces, where it drips off before it can really soak in and do its thing.The sprayer is excellent and strong, but must be turned completely to the desired setting or it's weak and resistant. I thought it was a problem with the sprayer before I realized I was between settings.Overall, great product that makes light work of those dreaded once-a-year kitchen jobs.