I don't use the DN-77, but on the super duper bad jobs that Nano (UP Extreme. I call it Nano) kicks ass. I call it my Nuclear Option. My Mongolian Restaurant owners are very impressed with my results.
I've got my favourite/cheap kitchen degreaser that I boost around 1/3 in my HF its awesome on restaurants and rinses easily... cant say they all rinse easily but for an extra $1 a HF its great