It doesn't make the stuff just fall away like an overnight soak. Still takes some elbow grease to loosen the ring, but the PBW makes it easier.
In my case it's just the nature of my brewery. I've got one big (seven gallons? never measured) glass carboy that is my primary (lucky score off newspaper classifieds), and then several five gallon ones that I use as secondaries. The primary is big enough that I don't need a blowoff tube.
I try to reuse my yeast when possible, so I rack and brew on the same day when I can. I'll do a string of three to five brews off one packet of Safale/Saflager.
At some point during the brew day I will rack from the primary, reserve some sludge to seed the next batch, then I need to clean the primary since I will need it again soon. I give it a rinse with the bottle washer to get all but the stuck stuff off, sprinkle in a spoon of PBW powder, add enough water to dissolve it, then shake it up whenever I walk past it, until it the boil is close to being over. I chill using the same spigot I use for the bottle washer, so I need a clean primary vessel before the boil is over. Can't clean and chill at the same time. So I use the brush to clean, and the bottle washer to rinse. After that the spigot is free for chilling. Don't want to start cleaning when the chill is over. A clean vessel should be ready to go.
When cleaning secondary vessels, I sometimes do an overnight soak, and use a racking cane to aid in pouring the stuff out. But I've only got one big glass carb for a primary, so by necessity I have learned to clean it without filling it and letting it soak overnight.